Examining the causal relationship between circulating immune cells and the susceptibility to osteomyelitis: A Mendelian randomization study

BACKGROUND

Osteomyelitis is considered as a deleterious inflammatory condition affecting the bone, primarily attributed to pathogenic infection. However, the underlying factors predisposing individuals to osteomyelitis remain incompletely elucidated. The immune system plays a multifaceted role in the progression of this condition, yet previous observational studies and randomized controlled trials investigating the association between circulating immune cell counts and osteomyelitis have been constrained. In order to address this knowledge gap, we conducted a Mendelian randomization (MR) analysis to evaluate the impact of diverse immune cell counts on the risk of developing osteomyelitis.

METHODS

In our study, we utilized single nucleotide polymorphisms (SNPs) that have been strongly linked to circulating immune cells or specific lymphocyte subtypes, as identified in large-scale genome-wide association studies (GWAS). These SNPs served as instrumental variables (IVs) for our MR analysis. We employed a more relaxed clumping threshold to conduct MR analysis on several related lymphocyte subtypes. To estimate causal effects, we utilized the Wald ratio, as well as the random-effects inverse variance weighted (IVW) and weighted median (WM) methods. To enhance the credibility of our results, we performed F-statistic calculations and a series of sensitivity analyses.

RESULTS

Our findings revealed a significant correlation between the absolute count of circulating lymphocytes and the risk of osteomyelitis [odds ratio(OR) 1.20；95 % confidence interval (CI), 1.08-1.32；P = 0.0005]. Furthermore, we identified a causal relationship between the absolute count of CD8+ T cells and susceptibility to osteomyelitis (OR 1.16; 95 % CI, 1.04-1.30; P = 0.0098). Importantly, these findings remained robust across a wide range of sensitivity analyses.

CONCLUSION

Through our MR analysis, we have provided evidence supporting a causal relationship between genetic predisposition to higher circulating immune cell counts and an increased risk of osteomyelitis. Specifically, our findings highlight the association between elevated CD8+ T cell counts and a heightened susceptibility to osteomyelitis. These results offer valuable insights for the future exploration of immunotherapy approaches in the management of osteomyelitis.

P2RX7 gene variants associate with altered inflammasome assembly and reduced pyroptosis in chronic nonbacterial osteomyelitis (CNO)

Chronic nonbacterial osteomyelitis (CNO), an autoinflammatory bone disease primarily affecting children, can cause pain, hyperostosis and fractures, affecting quality-of-life and psychomotor development. This study investigated CNO-associated variants in P2RX7, encoding for the ATP-dependent trans-membrane K+ channel P2X7, and their effects on NLRP3 inflammasome assembly. Whole exome sequencing in two related transgenerational CNO patients, and target sequencing of P2RX7 in a large CNO cohort (N = 190) were conducted. Results were compared with publicly available datasets and regional controls (N = 1873). Findings were integrated with demographic and clinical data. Patient-derived monocytes and genetically modified THP-1 cells were used to investigate potassium flux, inflammasome assembly, pyroptosis, and cytokine release. Rare presumably damaging P2RX7 variants were identified in two related CNO patients. Targeted P2RX7 sequencing identified 62 CNO patients with rare variants (32.4%), 11 of which (5.8%) carried presumably damaging variants (MAF <1%, SIFT "deleterious", Polyphen "probably damaging", CADD >20). This compared to 83 of 1873 controls (4.4%), 36 with rare and presumably damaging variants (1.9%). Across the CNO cohort, rare variants unique to one (Median: 42 versus 3.7) or more (≤11 patients) participants were over-represented when compared to 190 randomly selected controls. Patients with rare damaging variants more frequently experienced gastrointestinal symptoms and lymphadenopathy while having less spinal, joint and skin involvement (psoriasis). Monocyte-derived macrophages from patients, and genetically modified THP-1-derived macrophages reconstituted with CNO-associated P2RX7 variants exhibited altered potassium flux, inflammasome assembly, IL-1β and IL-18 release, and pyroptosis. Damaging P2RX7 variants occur in a small subset of CNO patients, and rare P2RX7 variants may represent a CNO risk factor. Observations argue for inflammasome inhibition and/or cytokine blockade and may allow future patient stratification and individualized care.

Osteomyelitis and non-coding RNAS: A new dimension in disease understanding

Osteomyelitis, a debilitating bone infection, presents considerable clinical challenges due to its intricate etiology and limited treatment options. Despite strides in surgical and chemotherapeutic interventions, the treatment landscape for osteomyelitis remains unsatisfactory. Recent attention has focused on the role of non-coding RNAs (ncRNAs) in the pathogenesis and progression of osteomyelitis. This review consolidates current knowledge on the involvement of distinct classes of ncRNAs, including microRNAs, long ncRNAs, and circular RNAs, in the context of osteomyelitis. Emerging evidence from various studies underscores the potential of ncRNAs in orchestrating gene expression and influencing the differentiation of osteoblasts and osteoclasts, pivotal processes in bone formation. The review initiates by elucidating the regulatory functions of ncRNAs in fundamental cellular processes such as inflammation, immune response, and bone remodeling, pivotal in osteomyelitis pathology. It delves into the intricate network of interactions between ncRNAs and their target genes, illuminating how dysregulation contributes to the establishment and persistence of osteomyelitic infections. Understanding their regulatory roles may pave the way for targeted diagnostic tools and innovative therapeutic interventions, promising a paradigm shift in the clinical approach to this challenging condition. Additionally, we delve into the promising therapeutic applications of these molecules, envisioning novel diagnostic and treatment approaches to enhance the management of this challenging bone infection.

Chronic osteomyelitis risk is associated with NLRP3 gene rs10754558 polymorphism in a Chinese Han Population

BACKGROUND

Single nucleotide polymorphisms (SNPs) in the nucleotide-binding domain leucine-rich repeat protein-3 (NLRP3) gene are reported to be linked to many inflammatory disorders. However, uncertainty persists over the associations between these SNPs and susceptibilities to chronic osteomyelitis (COM). This study aimed to investigate potential relationships between NLRP3 gene SNPs and the risks of developing COM in a Chinese Han cohort.

METHODS

The four tag SNPs of the NLRP3 gene were genotyped in a total of 428 COM patients and 368 healthy controlsusing the SNapShot technique. The genotype distribution, mutant allele frequency, and the four genetic models (dominant, recessive, homozygous, and heterozygous) of the four SNPs were compared between the two groups.

RESULTS

A significant association was found between rs10754558 polymorphism and the probability of COM occurence by the heterozygous model (P = 0.037, odds ratio [OR] = 1.541, 95% confidence interval [CI] = 1.025-2.319), indicating that rs10754558 may be associated with a higher risk of developing COM.In addition, possible relationship was found between rs7525979 polymorphism and the risk of COM development by the outcomes of homozygous (P = 0.073, OR = 0.453, 95% CI = 0.187-1.097) and recessive (P = 0.093, OR = 0.478, 95% CI = 0.198-1.151) models, though no statistical differences were obtained.

CONCLUSIONS

Outcomes of the present study showed, for the first time, that rs10754558 polymorphism of the NLRP3 gene may increase the risk of COM development in this Chinese Han population, with genotype CG as a risk factor. Nonetheless, this conclusion requires verification from further studies with a larger sample size.

LPIN2 -related Majeed syndrome: report of two Indian patients with novel variants in LPIN2 and review of literature

LPIN2 -related Majeed syndrome (MIM# 609628) is a rare non-inflammasome autoinflammatory disease, caused due to biallelic variants in LPIN2 (MIM* 605519). To date, only 31 individuals from 18 families have been reported with this rare condition. Exome sequencing was done in two affected individuals from two unrelated families. Additionally, phenotypic, and genotypic information from the literature was reviewed. Two novel homozygous missense variants, c.2207G>A p. (Arg736His) and c.1157C>G p. (Ser386Ter) in LPIN2 , were identified in family 1 and family 2 respectively. Chronic recurrent osteomyelitis involving the lower extremities was the most common clinical presentation. LPIN2 -related Majeed syndrome should be considered as a differential diagnosis in an individual with clinical or radiological evidence of recurrent sterile osteomyelitis and chronic anaemia.

The role of NSAID in mediating the effect of genetically predicted major depressive disorder on osteomyelitis: A Mendelian randomization study

BACKGROUND

Osteomyelitis and major depressive disorder (MDD) are significant health concerns with potential interconnections. However, the underlying mechanisms linking these conditions remain unknown. This study aimed to investigate the potential mediating role of non-steroidal anti-inflammatory drug (NSAID) medication in the association between MDD and the risk of osteomyelitis.

METHODS

We utilized summary data from large-scale genome-wide association studies (GWAS) to perform Mendelian randomization (MR) mediation analysis. Instrumental variables were selected based on genome-wide significance, and instrumental strength was assessed using F-statistics. Univariable and multivariable MR analyses were conducted to estimate causal effects and proportions mediated by NSAID medication.

RESULTS

The univariable MR analysis revealed significant associations between MDD and osteomyelitis (odds ratio [OR] = 1.44, 95 % confidence interval [CI]: 1.18-1.874) and between MDD and NSAID medication (OR = 1.36, 95 % CI 1.24-1.49). In the multivariable MR analysis, the direct effect of MDD on osteomyelitis was OR 1.35 (95 % CI: 1.09, 1.67) after adjusting for NSAID medication. The proportion of mediation by NSAID medication was 23 % (95 % CI: 0.05 %, 38.6 %).

CONCLUSION

This MR study provides evidence for a genetically predicted causal association between MDD, NSAID medication, and osteomyelitis. The findings emphasize the need for a comprehensive approach in managing individuals with comorbid depression and osteomyelitis, considering the potential risks and benefits of NSAID medication. Future research should address limitations and explore additional mediators and confounding factors to enhance understanding of this complex relationship.

Exploring the pathogenesis of osteomyelitis accompanied by diabetic foot ulcers using microarray data analysis

Although numerous studies have shown distinctive similarities between osteomyelitis and diabetic foot ulcers (DFU), the common pathogenesis of both is not fully understood. The current research focuses on an in-depth study of the molecular and pathway mechanisms involved in the complication of these 2 diseases. We downloaded clinical information on osteomyelitis (GSE30119) and DFU (GSE29221) from the GEO database, along with gene expression matrices. Differentially expressed genes (DEGs) among normal individuals and patients with osteomyelitis; normal individuals and patients with DFU were identified by R software, and thus common DEGs were confirmed. We then analyzed these differential genes, including the functional pathway analysis, protein-protein interaction (PPI), modules and hub genes establishment, and transcription factor regulatory networks. We identified 109 common DEGs (46 up-regulated and 63 down-regulated genes) for subsequent analysis. The results of PPI network and the functional pathway analysis revealed the importance of immune response and inflammatory response in both diseases. Among them, chemokines and cytokines were found to be closely related to both osteomyelitis and DFU. In addition, the tumor necrosis factor (TNF) pathway and Staphylococcus aureus infection were found to have more significant roles too. The 12 most essential key genes were later screened by cytoHubba, including matrix metalloproteinases (MMP) 1, MMP3, MMP9, IL8, C-X-C chemokine receptor (CXCR) 2, C-X-C motif chemokine ligand (CXCL) 9, CXCL10, CXCL13, FCGR3B, IL1B, LCN2, S100A12. CXCL10, and MMP1 were validated using the least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE) algorithms. Osteomyelitis and DFU share similar molecular and pathway mechanisms. These common key genes and pathways may provide new directions toward the future study of osteomyelitis and DFU.

DNMT1-mediated DNA methylation in toll-like receptor 4 (TLR4) inactivates NF-κB signal pathway-triggered pyroptotic cell death and cellular inflammation to ameliorate lipopolysaccharides (LPS)-induced osteomyelitis

Toll-like receptor 4 (TLR4) plays a critical role in various human diseases, and was associated with pyroptotic cell death and inflammatory responses. DNA methylation, which has stable and reversible properties, has been reported to alter the expression of target genes, including TLR4. However, the role of methylated TLR4 in osteomyelitis (OM) and the underlying molecular mechanisms remain unclear. RNA sequencing was used to identify differentially expressed genes and associated signaling pathways. RT-qPCR, Western blot, emzyme-linked immunosorbent assay (ELISA), cell counting kit-8 (CCK-8) and LDH assay kit were used to detect mRNA and protein expression of relevant genes, cell viability and the LDH activity, respectively. TLR4 methylation was detected by methylation-specific PCR (MSP) and verified by Chromatin immunoprecipitation (ChIP). Here, we found that DNA methyltransferase-1 (DNMT1)-mediated TLR4 demethylation significantly suppressed lipopolysaccharides (LPS)-induced pyroptosis and inflammatory response by inhibiting the TLR4/nuclear transcription factor-kappa B (NF-κB) axis. First, we confirmed TLR4 as the study target by mRNA transcriptome sequencing analysis, and TLR4 was observably high-expressed in both OM patients and LPS-treated osteoblastic MC3T3-E1. Then, we found that downregulation of DNMT1 blocked TLR4 promoter methylation modification, resulting in upregulation of TLR4. Simultaneously, functional experiments indicated that suppression of TLR4 or overexpression of DNMT1 promoted cell proliferation and inhibited cell pyroptosis and inflammation in LPS-induced MC3T3-E1, while upregulation of TLR4 restored the effects of DNMT1 silencing on OM progression. In addition, TLR4 elevated phosphorylation of IκB-α and NF-κB p65 in the NF-κB signal pathway, and inhibition of TLR4 or the NF-κB inhibitor PDTC reversed the influence of inhibition of DNMT1. In conclusion, our study demonstrated that DNMT1-mediated TLR4 DNA methylation alleviated LPS-induced OM by inhibiting the NF-κB signaling pathway.

Global Transcriptomic Study of Circular-RNA Expression Profile in Osteoclasts Infected by Intracellular Staphylococcus aureus

Osteomyelitis is difficult to cure, and the rapidly rising morbidity is a thorny problem accompanied by a large number of joint replacement applications. Staphylococcus aureus is the main pathogen of osteomyelitis. Circular RNAs (circRNAs), as emerging noncoding RNAs, play important roles in multiple physiopathological processes which could provide novel insights into osteomyelitis. However, little is known about the roles of circRNAs in the pathogenesis of osteomyelitis. Osteoclasts, considered bone sentinels, are the resident macrophages in bone and may play the immune defense roles in osteomyelitis. It has been reported that S. aureus can survive in osteoclasts, but the function of osteoclast circRNAs in response to intracellular S. aureus infection remains unclear. In this study, we investigated the profile of circRNAs in osteoclasts infected by intracellular S. aureus through high-throughput RNA sequencing. In total, 24 upregulated and 62 downregulated differentially expressed circRNAs were identified and subsequently analyzed to demonstrate their potential functions. On this basis, three circRNAs (chr4:130718154-130728164+, chr8:77409548-77413627-, and chr1:190871592-190899571-) were confirmed as potential novel biomarkers for the diagnosis of osteomyelitis through the murine model of osteomyelitis. Most importantly, we verified that the circRNA chr4:130718154-130728164+ named circPum1 could regulate the host autophagy to affect the intracellular infection of S. aureus through miR-767. In addition, circPum1 could serve as a promising serum biomarker in osteomyelitis patients caused by S. aureus infection. Taken together, this study provided the first global transcriptomic profile analysis of circRNAs in osteoclasts infected by intracellular S. aureus and first proposed a novel perspective for the pathogenesis and immunotherapy of S. aureus-induced osteomyelitis from the term of circRNAs.

Genomic characterization of Staphylococcus aureus isolates causing osteoarticular infections in otherwise healthy children

Background

Pediatric osteoarticular infections are commonly caused by Staphylococcus aureus. The contribution of S. aureus genomic variability to pathogenesis of these infections is poorly described.

Methods

We prospectively enrolled 47 children over 3 1/2 years from whom S. aureus was isolated on culture—12 uninfected with skin colonization, 16 with skin abscesses, 19 with osteoarticular infections (four with septic arthritis, three with acute osteomyelitis, six with acute osteomyelitis and septic arthritis and six with chronic osteomyelitis). Isolates underwent whole genome sequencing, with assessment for 254 virulence genes and any mutations as well as creation of a phylogenetic tree. Finally, isolates were compared for their ability to form static biofilms and compared to the genetic analysis.

Results

No sequence types predominated amongst osteoarticular infections. Only genes involved in evasion of host immune defenses were more frequently carried by isolates from osteoarticular infections than from skin colonization (p = .02). Virulence gene mutations were only noted in 14 genes (three regulating biofilm formation) when comparing isolates from subjects with osteoarticular infections and those with skin colonization. Biofilm results demonstrated large heterogeneity in the isolates’ capacity to form static biofilms, with healthy control isolates producing more robust biofilm formation.

Conclusions

S. aureus causing osteoarticular infections are genetically heterogeneous, and more frequently harbor genes involved in immune evasion than less invasive isolates. However, virulence gene carriage overall is similar with infrequent mutations, suggesting that pathogenesis of S. aureus osteoarticular infections may be primarily regulated at transcriptional and/or translational levels.

The Underlying Molecular Basis and Mechanisms of Venous Thrombosis in Patients with Osteomyelitis: A Data-Driven Analysis

Objective

Osteomyelitis (OM) is one of the most risky and challenging diseases. Emerging evidence indicates OM is a risk factor for increasing incidence of venous thromboembolism (VTE) development. However, the mechanisms have not been intensively investigated.

Methods

The OM-related dataset GSE30119 and VTE-related datasets GSE19151 and GSE48000 were downloaded from the Gene Expression Omnibus (GEO) database and analyzed to identify the differentially expressed genes (DEGs) (OMGs1 and VTEGs1, respectively). Functional enrichment analyses of Gene Ontology (GO) terms were performed. VTEGs2 and OMGs2 sharing the common GO biological process (GO-BP) ontology between OMGs1 and VTEGs1 were detected. The TRRUST database was used to identify the upstream transcription factors (TFs) that regulate VTEGs2 and OMGs2. The protein-protein interaction (PPI) network between VTEGs2 and OMGs2 was constructed using the Search Tool for the Retrieval of Interacting Genes (STRING) database and then visualized in Cytoscape. Topological properties of the PPI network were calculated by NetworkAnalyzer. The Molecular Complex Detection (MCODE) plugin was utilized to perform module analysis and choose the hub modules of the PPI network.

Results

A total of 587 OMGs1 and 382 VTEGs1 were identified from the related dataset, respectively. GO-BP terms of OMGs1 and shared DGEs1 were mainly enriched in the neutrophil-related immune response process, and the shared GO-BP terms of OMGs1 and VTEGs1 seemed to be focused on cell activation, immune, defense, and inflammatory response to stress or biotic stimulus. 230 VTEGs2, 333 OMGs2, and 13 shared DEGs2 were detected. 3 TF-target gene pairs (SP1-LSP1, SPI1-FCGR1A, and STAT1-FCGR1A) were identified. The PPI network contained 1611 interactions among 467 nodes. The top 10 hub proteins were TP53, IL4, MPO, ELANE, FOS, CD86, HP, SOCS3, ICAM1, and SNRPG. Several core nodes (such as MPO, ELANE, and CAMP) were essential components of the neutrophil extracellular traps (NETs) network.

Conclusion

This is the first data-mining study to explore shared signatures between OM and VTE by the integrated bioinformatic approach, which can help uncover potential biomarkers and therapeutic targets of OM-related VTE.

Local and Systemic Cytokine, Chemokine, and FGF Profile in Bacterial Chondronecrosis with Osteomyelitis (BCO)-Affected Broilers

Complex disease states, like bacterial chondronecrosis with osteomyelitis (BCO), not only result in physiological symptoms, such as lameness, but also a complex systemic reaction involving immune and growth factor responses. For the modern broiler (meat-type) chickens, BCO is an animal welfare, production, and economic concern involving bacterial infection, inflammation, and bone attrition with a poorly defined etiology. It is, therefore, critical to define the key inflammatory and bone-related factors involved in BCO. In this study, the local bone and systemic blood profile of inflammatory modulators, cytokines, and chemokines was elucidated along with inflammasome and key FGF genes. BCO-affected bone showed increased expression of cytokines IL-1β, while BCO-affected blood expressed upregulated TNFα and IL-12. The chemokine profile revealed increased IL-8 expression in both BCO-affected bone and blood in addition to inflammasome NLRC5 being upregulated in circulation. The key FGF receptor, FGFR1, was significantly downregulated in BCO-affected bone. The exposure of two different bone cell types, hFOB and chicken primary chondrocytes, to plasma from BCO-affected birds, as well as recombinant TNFα, resulted in significantly decreased cell viability. These results demonstrate an expression of proinflammatory and bone-resorptive factors and their potential contribution to BCO etiology through their impact on bone cell viability. This unique profile could be used for improved non-invasive detection of BCO and provides potential targets for treatments.

VARIANTS OF IL1 (C3954T, RS1143634), PON1 (C108T, RS705379) GENES AS PROGNOSTIC MARKERS OF OSTEOMYELITIS RISK AND ITS COMPLICATIONS

The aim of the work was to study the effect of IL1Β (C3954T, rs1143634), PON1 (C108T, rs705379) gene variants on the risk of bacterial osteomyelitis development and its complicated course. The study involved 56 patients with osteomyelitis - 20 with not complicated (non-recurrent) course after treatment and 36 with complicated (recurrent) course. The data of population frequencies for the European population, obtained from the open database of "1000 Genomes project", were used as a control group. There was significantly increased distribution frequency of genotype 3954TT of IL1Β in patients with uncomplicated course compared to the control group (χ2=6.05, p=0.014, OR=4.99 (1.55-16.07)). And was found increased of minor genotype 108TT of PON1 frequency in patients with osteomyelitis compared to control group (χ2=4.38, p=0.036, OR=1.85(1.03-3.33)). There were found gender differences in the clinical effects of IL1Β gene variant: in men, the prevalence of genotype 3954CC was significantly to be increased in the patient with complicated osteomyelitis; genotype 3954CT was associated with a reduced risk of osteomyelitis and its complications developing, while in women was found the association of genotype 3954TT with an uncomplicated course of the disease. In conclusion, this study suggests that the variants of IL1В and PON1 genes associated with the risk of developing bacterial osteomyelitis and its complicated course and can be used as a prognostic marker for developing personalized prevention strategies.

Deficiency of Lipin2 Results in Enhanced NF-κB Signaling and Osteoclast Formation in RAW-D Murine Macrophages

Lipin2 is a phosphatidate phosphatase that plays critical roles in fat homeostasis. Alterations in Lpin2, which encodes lipin2, cause the autoinflammatory bone disorder Majeed syndrome. Lipin2 limits lipopolysaccharide (LPS)-induced inflammatory responses in macrophages. However, little is known about the precise molecular mechanisms underlying its anti-inflammatory function. In this study, we attempted to elucidate the molecular link between the loss of lipin2 function and autoinflammatory bone disorder. Using a Lpin2 knockout murine macrophage cell line, we showed that lipin2 deficiency enhances innate immune responses to LPS stimulation through excessive activation of the NF-κB signaling pathway, partly because of TAK1 signaling upregulation. Lipin2 depletion also enhanced RANKL-mediated osteoclastogenesis and osteoclastic resorption activity accompanied by NFATc1 dephosphorylation and increased nuclear accumulation. These results suggest that lipin2 suppresses the development of autoinflammatory bone disorder by fine-tuning proinflammatory responses and osteoclastogenesis in macrophages. Therefore, this study provides insights into the molecular pathogenesis of monogenic autoinflammatory bone disorders and presents a potential therapeutic intervention.

Shorter Telomere Length in Peripheral Blood Leukocytes Is Associated with Post-Traumatic Chronic Osteomyelitis

Background: This study investigated the association between post-traumatic chronic osteomyelitis (COM) and peripheral leukocyte telomere length (PLTL) and explored factors associated with PLTL in COM. Methods: A total of 56 patients with post-traumatic COM of the extremity and 62 healthy control subjects were recruited. The PLTL was measured by real-time PCR. Binary logistic regression analysis was used to identify factors in correlation with telomere length. Sex, age, white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and infection duration were included as independent variables in the logistic regression model. Results: Post-traumatic COM patients had significantly shorter PLTLs (5.39 ± 0.40) than healthy control subjects (5.69 ± 0.46; p < 0.001). Binary logistic regression analysis showed that PLTL had a statistically significant association with age (B = -0.072; p = 0.013) and CRP (B = -0.061; p = 0.033). The logistic regression model was statistically significant and explained 31.4% (Nagelkerke R²) of the change in telomere length and correctly classified 69.6% of the cases. Conclusions: Patients with post-traumatic COM have shorter PLTLs than healthy subjects. The PLTL erosion of post-traumatic COM was partially explained by age and CRP.

Osteosarcoma of the Mandible in a Patient with Florid Cemento-Osseous Dysplasia and Li-Fraumeni Syndrome: A Rare Coincidence

Cemento-osseous dysplasia (COD) is the most common benign fibro-osseous lesion of the jaws and generally considered non-neoplastic and self-limited. Here, we present a 30-year old female who noticed a bilateral swelling of her posterior mandible with irregular periapical mineralization and incomplete root resorption on panoramic radiographs. A biopsy revealed florid COD and no further treatment was initiated. 9 years later, she presented with a progressive expansion of her left posterior mandible after being treated for bilateral breast cancer 4 and 8 years before. CT scans showed expansile and densely mineralized lesions in all four quadrants with the left posterior mandible showing a focal penetration of the buccal cortical bone. Biopsies revealed an osteoblastic high-grade osteosarcoma in the left and a COD in the right mandible, notably with cellular atypia in the spindle cell component. The patient underwent segmental resection of the left mandible with clear margins and adjuvant chemotherapy. Subsequent genetic testing identified a heterozygous germline TP53 mutation (p.V173G) which confirmed the clinically suspected Li-Fraumeni syndrome (LFS). 3 years after the resection, the patient is free of disease and the other foci of COD remained stable in size on follow-up imaging analyses. Our case illustrates LFS-related osteosarcoma developing within florid COD. Given the rarity of this coincidence, a causative relation between the two lesions seems unlikely but in patients with tumor predisposition syndromes it might be advisable to closely monitor even benign lesions like COD.

Chronic non-bacterial osteomyelitis: another disease associated with MEFV gene mutations

OBJECTIVES

Chronic non-bacterial osteomyelitis (CNO) is an autoinflammatory bone disease of unknown aetiology. The relationship between CNO and familial Mediterranean fever (FMF) is not clearly documented so far. This cross-sectional study aims to evaluate the clinical and laboratory characteristics of a cohort of CNO patients within the context of its relationship with FMF and MEFV gene mutations.

METHODS

Demographic and clinical data were extracted from electronic medical records of patients with CNO. The MEFV gene analysis was performed for all patients.

RESULTS

A total number of 18 patients with CNO with a median follow-up of 36.50 (13.00-84.00) months were included in the study. Five patients (27.8%) were found to have at least one exon 10 mutations (four with M694V and one with M680I). Four of them (22.2%) had homozygous or compound heterozygous mutations of the MEFV gene. Two patients had a previous diagnosis of FMF and developed CNO while FMF was under control. Patients with MEFV mutations had an earlier onset of CNO, higher acute phase reactants, lower haemoglobin concentrations, and a higher number of bone lesions at disease onset with a persistent course of disease more frequently.

CONCLUSIONS

Our results demonstrated an increased frequency of MEFV gene mutations in CNO and a more severe disease phenotype of CNO in patients with MEFV gene mutations. Physicians practicing in regions where FMF is prevalent should be aware of this relationship and ask about the symptoms of FMF in detail in patients with CNO. Moreover, FMF should be included in CNO-associated conditions.

Dysregulated NADPH Oxidase Promotes Bone Damage in Murine Model of Autoinflammatory Osteomyelitis

Autoinflammatory diseases are characterized by dysregulation of the innate immune system, leading to spontaneous inflammation. Pstpip2cmo mouse strain is a well-characterized model of this class of disorders. Because of the mutation leading to the lack of adaptor protein PSTPIP2, these animals suffer from autoinflammatory chronic multifocal osteomyelitis similar to several human syndromes. Current evidence suggests that it is driven by hyperproduction of IL-1β by neutrophil granulocytes. In this study, we show that in addition to IL-1β, PSTPIP2 also negatively regulates pathways governing reactive oxygen species generation by neutrophil NOX2 NADPH oxidase. Pstpip2cmo neutrophils display highly elevated superoxide production in response to a range of stimuli. Inactivation of NOX2 NADPH oxidase in Pstpip2cmo mice did not affect IL-1β levels, and the autoinflammatory process was initiated with similar kinetics. However, the bone destruction was almost completely alleviated, suggesting that dysregulated NADPH oxidase activity is a key factor promoting autoinflammatory bone damage in Pstpip2cmo mice.

Recessive mutation in GALNT3 causes hyperphosphatemic familial tumoral calcinosis associated with chronic recurrent multifocal osteomyelitis

Albaramki J, Dmour H, Shboul M, Bonnard C, Venkatesh B, Odeh R. Recessive mutation in GALNT3 causes hyperphosphatemic familial tumoral calcinosis associated with chronic recurrent multifocal osteomyelitis. Turk J Pediatr 2019; 61: 130-133. Hyperphosphatemic familial tumoral calcinosis is a rare autosomal recessive disorder that is characterized by persistent hyperphosphatemia and extra-articular calcifications. Three cases were previously reported with hyperphosphatemic familial tumoral calcinosis that were associated with chronic recurrent multifocal osteomyelitis, an autoinflammatory disorder that is characterized by recurrent episodes of bone pain. We describe here an 11-year-old child who was diagnosed with these two conditions and was found to carry a splice site mutation c.1524+1G > A in the GALNT3 gene.

WNT6 is an effective marker for osteosarcoma diagnosis and prognosis

Wingless-Type MMTV Integration Site Family, Member 6 (WNT6) is a member of the Wnt family and its expression is abnormal in different human cancer cell lines. The purpose of this study was to investigate the clinical significance of WNT6 in osteosarcoma.The levels of WNT6 mRNA and protein in tissue and serum were detected through quantitative real-time polymorperase chain reaction (qRT-PCR) and Enzyme Lined Immunosorbent Assay (ELISA), respectively. Chi-square test was performed to estimate the association of WNT6 expression with clinical parameters among osteosarcoma patients. Receiver operation characteristic (ROC) curve was plotted to determine diagnostic performance of serum WNT6 in osteosarcoma. Survival analysis was performed using Kaplan-Meier method. Cox regression analysis was adopted to evaluate prognostic significance of WNT6 expression among osteosarcoma patients.Compared with the controls, WNT6 mRNA and protein levels were significantly elevated in patients with osteosarcoma (P > .05 for all). Furthermore, WNT6 upregulation showed positive correlation with patients' age (P < .001), tumor grade (P < .001) and distant metastasis (P = .001). WNT6 might be a diagnostic marker for osteosarcoma with an AUC of 0.854 combining a specificity of 88.4% and a sensitivity of 77.8%. Survival analysis result indicated that high WNT6 expression predicted poor survival (log rank test, P = .001). WNT6 might be a potential prognostic biomarker for osteosarcoma (HR = 2.227, 95%CI = 1.061-10.842, P = .027).WNT6 may be a diagnostic and prognostic marker in osteosarcoma.

Examining the association of MMP-1 gene -1607 (2G/1G) and -519 (A/G) polymorphisms with the risk of osteomyelitis: A case-control study

To investigate the effects of matrix metalloproteinase-1 (MMP-1) gene polymorphisms on the onset of osteomyelitis in Chinese Han population.In all, 80 osteomyelitis patients (case group) and 81 healthy people (control group) were recruited into this case-control study. Polymerase chain reaction-restriction fragment length polymorphism method was utilized to examine the genotypes of MMP-1 polymorphisms (-1607 2G/1G and -519A/G) in the 2 groups. Genotype and allele differences between the case and control groups were analyzed by chi-square test. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to present the association strength between MMP-1 gene polymorphisms and osteomyelitis.Frequencies of -1607 2G/2G genotype between the case and control groups were statistically significant (P = .025). Compared with 1G/1G genotype carriers, the 2G/2G genotype carriers had 1.605 times risk of developing osteomyelitis (OR 2.605, 95% CI 1.116-6.082). Meanwhile, the 2G allele significantly associated with the risk of osteomyelitis (OR 1.735, 95% CI 1.115-2.701). In addition, frequency of -519GG genotype was obviously higher in case group than that in control group (P = .024), and GG genotype related to an increased risk of osteomyelitis (OR 2.792, 95% CI 1.127-6.917). Whereas, the -519G allele may be a susceptible factor for osteomyelitis (OR 1.622, 95% CI 1.038-2.536).The MMP-1 -1607 (2G/1G) and -519 (A/G) polymorphisms may contribute to the onset of osteomyelitis.

Dermatologic Manifestations of Monogenic Autoinflammatory Diseases

Autoinflammatory disorders are sterile inflammatory conditions characterized by episodes of early-onset fever, rash, and disease-specific patterns of organ inflammation. Gain-of-function mutations in innate danger-sensing pathways, including the inflammasomes and the nucleic acid sensing pathways, play critical roles in the pathogenesis of IL-1 and Type-I IFN-mediated disorders and point to an important role of excessive proinflammatory cytokine signaling, including interleukin (IL)-1b , Type-I interferons, IL-18, TNF and others in causing the organ specific immune dysregulation. The article discusses the concept of targeting proinflammatory cytokines and their signaling pathways with cytokine blocking treatments that have been life changing for some patients.

Recessive coding and regulatory mutations in FBLIM1 underlie the pathogenesis of chronic recurrent multifocal osteomyelitis (CRMO)

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare, pediatric, autoinflammatory disease characterized by bone pain due to sterile osteomyelitis, and is often accompanied by psoriasis or inflammatory bowel disease. There are two syndromic forms of CRMO, Majeed syndrome and DIRA, for which the genetic cause is known. However, for the majority of cases of CRMO, the genetic basis is unknown. Via whole-exome sequencing, we detected a homozygous mutation in the filamin-binding domain of FBLIM1 in an affected child with consanguineous parents. Microarray analysis of bone marrow macrophages from the CRMO murine model (cmo) determined that the Fblim1 ortholog is the most differentially expressed gene, downregulated over 20-fold in the cmo mouse. We sequenced FBLIM1 in 96 CRMO subjects and found a second proband with a novel frameshift mutation in exon 6 and a rare regulatory variant. In SaOS2 cells, overexpressing the regulatory mutation showed the flanking region acts as an enhancer, and the mutation ablates enhancer activity. Our data implicate FBLIM1 in the pathogenesis of sterile bone inflammation and our findings suggest CRMO is a disorder of chronic inflammation and imbalanced bone remodeling.

Missense splice variant (g.20746A>G, p.Ile183Val) of interferon gamma receptor 1 (IFNGR1) coincidental with mycobacterial osteomyelitis - a screen of osteoarticular lesions

Previously, dominant partial interferon-gamma receptor 1 (IFN-g-R1) susceptibility to environmental mycobacteria was found with IFNGR1 deletions or premature stop. Our aim was to search for IFNGR1 variants in patients with mycobacterial osteoarticular lesions. Biopsies from the patients were examined for acid-fast bacilli, inflammatory cell infiltration, and mycobacterial niacin. Mycobacterial rRNA was analyzed using a target-amplified rRNA probe test. Peripheral-blood-leukocyte genomic DNA was isolated from 19 patients using the QIAamp DNA Mini Kit, and all IFNGR1 exons were sequenced using an ABIPRISM 3130 device. After the discovery of an exon 5 variant, a Polish newborn population sample (n = 100) was assayed for the discovered variant. Splice sites and putative amino acid interactions were analyzed. All patients tested were positive for mycobacteria; one was heterozygous for the IFNGR1 exon 5 single-nucleotide-missense substitution (g.20746A>G, p.Ile183Val). No other variant was found. The splice analysis indicated the creation of an exonic splicing silencer, and alternatively, molecular graphics indicated that the p.Ile183Val might alter beta-strand packing (loss of van der Waals contacts; Val183/Pro205), possibly altering the IFN-g-R1/IFN-g-R2 interaction. The probability of non-deleterious variant was estimated as <10%. Heterozygous IFNGR1:p.Ile183Val (frequency 0.003%) was found to be coincidental with mycobacterial osteomyelitis. The small amount of variation detected in the patients with osteoarticular lesions indicates that screens should not yet be restricted: Intronic variants should be analyzed as well as the other genes affecting Type 1 T-helper-cell-mediated immunity.

Phenol-Soluble Modulins Contribute to Early Sepsis Dissemination Not Late Local USA300-Osteomyelitis Severity in Rabbits

Introduction

In bone and joint infections (BJIs), bacterial toxins are major virulence factors: Panton—Valentine leukocidin (PVL) expression leads to severe local damage, including bone distortion and abscesses, while α-hemolysin (Hla) production is associated with severe sepsis-related mortality. Recently, other toxins, namely phenol-soluble modulins (PSMs) expressed by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain USA300 (LAC WT) were shown to have ex vivo intracellular cytotoxic activity after S. aureus invasion of osteoblasts, but their in vivo contribution in a relatively PVL-sensitive osteomyelitis model remains poorly elucidated.

Materials and Methods

We compared the outcomes of experimental rabbit osteomyelitises induced with pvl⁺hla⁺psms⁺ LAC WT and its isogenic Δpsm derivatives (LAC Δpsmα and LAC Δpsmαβhld) using an inoculum of 3 × 10⁸ CFUs. Mortality, hematogenous spread (blood culture, spleen and kidney), lung and bone involvements were assessed in two groups (non-survivors of severe sepsis and survivors sacrificed on day (D) 14).

Results

Severe sepsis-related mortality tended to be lower for Δpsm derivatives (Kaplan—Meier curves, P = .06). Non-survivors’ bone LAC-Δpsmα (6.9 log₁₀ CFUs/g of bone, P = .04) or -Δpsmαβhld (6.86 log₁₀ CFUs/g of bone, P = .014) densities were significantly higher than LAC WT (6.43 log₁₀ CFUs/g of bone). Conversely, lung Δpsmαβhld CFUs were significantly lower than LAC WT (P = .04). LAC Δpsmα, Δpsmαβhld and WT induced similar bone damage in D14 survivors, with comparable bacterial densities (respectively: 5.89, 5.91, and 6.15 log₁₀ CFUs/g of bone). Meanwhile, pulmonary histological scores of inflammation were significantly higher for LAC Δpsmα- and Δpsmαβhld-infected rabbits compared to LAC WT (P = .04 and .01, respectively) but with comparable lung bacterial densities.

Conclusion

Our experimental results showed that deactivating PSM peptides significantly limited bacterial dissemination from bone during the early phase of infection, but did not affect local severity of USA300 rabbit osteomyelitis.

Disseminated Mycobacterium avium complex infection in a child with partial dominant interferon gamma receptor 1 deficiency in India

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare condition characterized by clinical disease caused by weakly virulent mycobacteria. All genes mutated in MSMD patients are involved in IFN-γ immunity. Autosomal partial dominant (PD) interferon-γ receptor 1 (IFN-γR1) deficiency is the most frequent abnormality affecting the group of MSMD patients leading to impaired response of IFN-γ. We describe here a patient from India with disseminated infection due to Mycobacterium avium intracellulare (MAC) including multifocal osteomyelitis and BCG disease. A heterozygous mutation in exon 6 of IFNGR1 gene was identified, conferring an autosomal PD IFN-γR1 deficiency. Patient had recurrence of mycobacterial disease during antibiotic therapy for which subcutaneous IFN-γ was added as a modality of treatment for resistant MAC infection.

Gene expression analysis of children with acute hematogenous osteomyelitis caused by Methicillin-resistant Staphylococcus aureus: correlation with clinical severity of illness

Children with acute hematogenous osteomyelitis (AHO) demonstrate a broad spectrum of clinical manifestations, ranging from mild to severe. Several advances have been achieved in the study of host immune response to acute invasive Staphylococcus aureus infections through gene expression analysis. However, previous research has neither attempted to evaluate the response of children with AHO specific to Methicillin-resistant Staphylococcus aureus (MRSA) nor to correlate gene expression with clinical phenotype. Study objective was to correlate gene expression of children with AHO due to MRSA with clinical severity of illness. Whole blood samples were obtained in Tempus tubes from 12 children with osteomyelitis once cultures obtained directly from the site of infection confirmed to be positive for MRSA. Using an Illumina platform and a systems-wide modular analysis, microarray findings from ten of these children were compared to that of nine healthy (age, ethnicity and gender) matched controls and correlated with clinical severity of illness. Children with AHO from MRSA demonstrated over-expression of innate immunity with respect to neutrophil activity, coagulation, inflammatory response, and erythrocyte development. Concurrently, these children demonstrated under-expression of adaptive immunity with respect to lymphocyte activation and activity of T-cell, cytotoxic or NK cell, and B-cell lines. Three over-expressed genes, P2RX1, SORT1, and RETN, and two under-expressed genes, LOC641788 and STAT 4, were significantly correlated with severity of illness. STAT 4 showed the strongest correlation (R2 = –0.83). STAT4 downregulation could potentially explain under-expression of genes related to adaptive immunity in this cohort of patients with AHO. This study identified specific genes which correspond to disease severity during the early hospitalization of children with AHO from MRSA. Pattern recognition of this combination of genes could help to identify in the future severe clinical phenotypes before the disease is fully manifest and direct appropriate attention and resources to those children.

Exome sequencing reveals RAG1 mutations in a child with autoimmunity and sterile chronic multifocal osteomyelitis evolving into disseminated granulomatous disease

We describe a boy who developed autoinflammatory (chronic sterile multifocal osteomyelitis) and autoimmune (autoimmune cytopenias; vitiligo) phenotypes who subsequently developed disseminated granulomatous disease. Whole exome sequencing revealed homozygous RAG1 mutations thus expanding the spectrum of combined immunodeficiency with autoimmunity and granuloma that can occur with RAG deficiency.

Multifocal Tuberculous osteomyelitis: possible inherited interferon gamma axis defect

Multifocal Tuberculous (TB) osteomyelitis is an extremely rare entity in immunocompetent individuals. The authors report a 19-mo-old girl with multifocal TB osteomyelitis which resolved completely following institution of four drug antituberculous treatment for 1 y and detailed immunological evaluation was found to be normal but as the response of interferon gamma (IFN γ) in terms of production of IL12p40 was severely impaired, she is suggested to have a possible defect in the interferon gamma axis even though the exact defect in the pathway could not be delineated. This case report reiterates the need for detailed immunological evaluation in children presenting with multifocal TB osteomyelitis.

Autoinflammatory bone disorders

Autoinflammatory bone disorders are characterized by chronic non-infectious osteomyelitis and inflammation-induced bone resorption and result from aberrant activation of the innate immune system. Sporadic chronic non-bacterial osteomyelitis (CNO) is the most common disease subtype. The clinical picture is highly variable and the exact underlying pathophysiology remains to be determined. Recently, novel insights in the pathophysiology of sterile bone inflammation have been gathered by analyzing patients with rare, monogenic inflammatory diseases. In this overview CNO and Majeed syndrome, cherubism, hypophosphatasia and primary hypertrophic osteoarthropathy will be discussed. For the latter four disorders, a genetic cause affecting bone metabolism and leading to chronic bone inflammation has been described. The exact pathophysiology of CNO remains to be determined. Insights from monogenic autoinflammatory bone diseases and the identification of distinct inflammatory pathways may help to understand the pathogenesis of bone inflammation and inflammation-induced bone resorption in more common diseases.

Cryptococcal osteomyelitis in a child with a novel compound mutation of the IL12RB1 gene

The IL-12p40/IL-12Rbeta1 and IFN-gammaR1/IFN-gammaR2/STAT1 signaling pathways are important for clearing intracellular bacteria. Genetic defects within these pathways are associated with increased susceptibility to intracellular pathogens. Among these, IL-12Rbeta1 deficiency is the most common defect and leads to infections with Salmonella and Mycobacterium spp. We report a child who presented with Cryptococcal osteomyelitis and history of disseminated Mycobacterial infection and recurrent Salmonella septicemia. Flow cytometry showed defective expression of IL-12Rbeta1. Mutation analysis revealed a novel compound heterozygous mutation of IL12RB1, c.625C>T, p.Q209X was found in exon 7 on the paternal allele and c.710delC, p.P237HfsX5 was found in exon 8 on the maternal allele. As these mutations each result in a stop codon before the last spliceable exon, the transcripts likely underwent nonsense mediated decay, leading to a lack of IL12Rbeta1 expression on the cell surface and eradicating signaling via the IL12 signaling pathway.

Mutation screening of the IL-1 receptor antagonist gene in chronic non-bacterial osteomyelitis of childhood and adolescence

OBJECTIVES

Chronic non-bacterial osteomyelitis CNO is an inflammatory disorder of the musculoskeletal system with unknown etiology. In addition to bone inflammation, patients may present with inflammatory involvement of other tissues including, e.g., skin. Recently, a novel syndrome due to deficiency of interleukin-1 receptor antagonist (IL1RN), DIRA has been identified. Clinically the syndrome is characterized by neonatal onset of pustular dermatosis, periostitis and chronic sterile multifocal osteomyelitis, strongly resembling CNO. Homozygous mutations of IL1RN have been identified and resulted in a truncated protein that is not secreted, hence leaving the action of interleukin-1 unopposed.

METHODS

Because of similar clinical, radiological and histological features of CNO and DIRA, we hypothesized that both disorders might share a common autoinflammatory process. Thus, we searched for the presence of mutations in the interleukin-1 receptor antagonist gene in 60 patients diagnosed with CNO.

RESULTS

In one patient with chronic multifocal osteomyelitis a heterozygous missense variant: c.281G>T (p.Cys94Phe) was detected. In the other patients only frequent polymorphisms were found.

CONCLUSIONS

Our findings were not able to confirm mutations in IL1RN being an important contributing factor to the pathogenesis of CNO.

Partial recessive IFN-γR1 deficiency: genetic, immunological and clinical features of 14 patients from 11 kindreds

We report a series of 14 patients from 11 kindreds with recessive partial (RP)-interferon (IFN)-γR1 deficiency. The I87T mutation was found in nine homozygous patients from Chile, Portugal and Poland, and the V63G mutation was found in five homozygous patients from the Canary Islands. Founder effects accounted for the recurrence of both mutations. The most recent common ancestors of the patients with the I87T and V63G mutations probably lived 1600 (875-2950) and 500 (200-1275) years ago, respectively. The two alleles confer phenotypes that are similar but differ in terms of IFN-γR1 levels and residual response to IFN-γ. The patients suffered from bacillus Calmette-Guérin-osis (n= 6), environmental mycobacteriosis (n= 6) or tuberculosis (n= 1). One patient did not suffer from mycobacterial infections but had disseminated salmonellosis, which was also present in two other patients. Age at onset of the first environmental mycobacterial disease differed widely between patients, with a mean value of 11.25 ± 9.13 years. Thirteen patients survived until the age of 14.82 ± 11.2 years, and one patient died at the age of 7 years, 9 days after the diagnosis of long-term Mycobacterium avium infection and the initiation of antimycobacterial treatment. Up to 10 patients are currently free of infection with no prophylaxis. The clinical heterogeneity of the 14 patients was not clearly related to either IFNGR1 genotype or the resulting cellular phenotype. RP-IFN-γR1 deficiency is, thus, more common than initially thought and should be considered in both children and adults with mild or severe mycobacterial diseases.

Chinese patients with defective IL-12/23-interferon-gamma circuit in Taiwan: partial dominant interferon-gamma receptor 1 mutation presenting as cutaneous granuloma and IL-12 receptor beta1 mutation as pneumatocele

BACKGROUND

IL-12/23-interferon-gamma circuit enhances reactive oxygen species (ROS) synthesis in macrophage to attack intracellular pathogens such as mycobacteria and salmonella. Defective ROS in patients with chronic granulomatous disease (CGD) have increased susceptibility to these pathogens. However, patients with defective IL-12/23-interferon-gamma circuit rather than CGD are not recognized in Taiwan, endemic for tuberculosis and salmonella.

AIM

The purpose of this study was to identify Taiwanese patients with defective IL-12/23-IFN-gamma circuit.

PATIENTS AND METHODS

In a long-term molecular study of primary immunodeficiency diseases (PIDD), the tentative CGD patients presenting with Bacille Calmette-Guerin (BCG)-induced infection, refractory atypical mycobacterial cutaneous granuloma and osteomyelitis, recurrent salmonella sepsis, and pneumatocele were studied for the IL-12/23-IFN-gamma circuit. ROS was first measured to exclude CGD. Candidate genes of IL12RB1, IFNRG1, IL12p40, IFNRG2, signal transducer and activator of transcription-1, and NF-kappaB essential modulator and their encoding protein expressions were analyzed.

RESULTS

Of the 175 Taiwanese PIDD patients during a 28-year period, three patients from two unrelated families were identified with the hotspot INFRG1 deletion mutation (818del4) and had CGD features, presenting as cutaneous granuloma, and multiple osteomyelitis infected by non-tuberculosis mycobacteria, Mycobacteria avium complex and Mycobacterium scrofulaceum. Another with mis-sense IL12RB1 mutation (Arg211Pro) was noted as recurrent Salmonella enteritidis D sepsis and pneumatocele.

CONCLUSION

Patients with defective IL-12/23-IFN-gamma circuit may resemble or overlap CGD manifestations of refractory cutaneous atypical mycobacterial granuloma and salmonella pneumatocele.

Autoinflammatory bone disorders

PURPOSE OF REVIEW

This review provides an update on clinical, genetic, and immunologic aspects of the autoinflammatory bone disorders.

RECENT FINDINGS

Chronic noninfectious inflammation of the bone is a clinical feature of both chronic recurrent multifocal osteomyelitis and (to a lesser degree) cherubism. The genes responsible for Majeed syndrome (LPIN2), murine chronic multifocal osteomyelitis (pstpip2), and cherubism (SH3BP2 and possibly PTPN11) have been identified. Murine models of both chronic recurrent multifocal osteomyelitis and cherubism have demonstrated that the bone inflammation is mediated by hematopoietically derived cells and can occur in the absence of a functioning adaptive immune system. As the immunologic defects become better defined, the cells of the myeloid lineage are emerging as the primary players.

SUMMARY

Chronic multifocal osteomyelitis and cherubism are hereditary chronic inflammatory disorders in which bone is the primary inflammatory target. Recent genetic and immunologic discoveries demonstrate involvement of the innate immune system, which places these entities in the category of autoinflammatory disorders.

Chronic recurrent multifocal osteomyelitis: a concise review and genetic update

Chronic recurrent multifocal osteomyelitis is an autoinflammatory disorder characterized by bone pain and fever, a course of exacerbations and remissions, and a frequent association with other inflammatory conditions. Because its etiology is largely unknown, the diagnosis is still based on clinical criteria; treatment is empiric and not always successful. The diagnosis is supported by the presence of osteolytic lesions with surrounding sclerosis apparent on radiographs, and silent asymptomatic lesions frequently appear on nuclear scans. The histologic findings in bone biopsies are nonspecific, showing inflammatory changes with granulocytic infiltration. Several observations suggest the contribution of genetic factors to the etiology of chronic recurrent multifocal osteomyelitis. Indeed, mutations in LPIN2 cause a syndromic form of chronic recurrent multifocal osteomyelitis known as Majeed syndrome, while mutations in pstpip2 cause a murine form of the disorder. The roles played by LPIN2 and the human homolog of pstpip2, PSTPIP2, in the etiology of chronic recurrent multifocal osteomyelitis are uncertain but are currently being investigated. We emphasize the need to validate diagnostic clinical criteria and develop new pathogenesis-based targeted therapy.

Bax gene G(-248)A promoter polymorphism is associated with increased lifespan of the neutrophils of patients with osteomyelitis

BACKGROUND

Patients with osteomyelitis have a decreased rate of spontaneous apoptosis of their peripheral blood neutrophils. The G(-248)A polymorphism in the promoter region of the bax gene is associated with prolonged peripheral blood neutrophil survival in leukemic patients and may play some role in osteomyelitis.

METHODS

Bax G(-248)A promoter polymorphism was detected by DNA amplification using polymerase chain reaction, followed by restriction fragment length polymorphism analysis. Spontaneous apoptosis of peripheral blood neutrophils was measured by propidium iodide, annexin V, and flow cytometry, and Bax was quantified by Western blotting.

RESULTS

The bax promoter polymorphism A allele was significantly more frequent in 80 patients with osteomyelitis than in 220 healthy donors (18.1% vs. 10.6%, chi=4.84, odds ratio=1.81, 95% confidence interval=1.06-3.07, P=.028). Carriers of the A allele had a lower apoptotic rate of their peripheral blood neutrophils compared with noncarriers (33.3+/-16.7 vs. 43.1+/-3.1, P=.036). Patients with the AA genotype showed a lower expression of the Bax protein compared with carriers of other genotypes (P=.038).

CONCLUSIONS

Substitution of a nucleotide G-->A at position -248 in the bax gene was more frequent in patients with osteomyelitis and was associated with a longer lifespan of their peripheral blood neutrophils and lower Bax protein expression. These findings may play a role in the pathogenesis of osteomyelitis.

Association between haemoglobin variants S and C and Mycobacterium ulcerans disease (Buruli ulcer): a case-control study in Benin

Risk factors for Buruli ulcer (BU) are poorly understood. We conducted a case-control study in southern Benin to investigate the association between haemoglobin variants S or C and BU, and particularly the association between haemoglobinopathies HbSS/SC and BU osteomyelitis. We compared the haemoglobin genotype of 179 patients with BU and 44 with BU osteomyelitis to that of 242 community controls. We found no evidence of an increased risk of BU according to the presence of haemoglobin variants S and/or C [odds ratio adjusted for sex, age, region of residence and ethnicity: 1.24 (95% CI: 0.80-1.93), P = 0.34]. Haemoglobin variants S and C are unlikely to play a role in the BU burden. However, haemoglobinopathies HbSS/SC were more frequent among BU osteomyelitis patients than among controls (6.8% vs. 1.0%, Fisher's exact P-value = 0.045), which may suggest that those disorders facilitate growth of Mycobacterium ulcerans in the bone matrix.

A splice site mutation confirms the role of LPIN2 in Majeed syndrome

Majeed syndrome is an autoinflammatory disorder consisting of chronic recurrent multifocal osteomyelitis, congenital dyserythropoietic anemia, and neutrophilic dermatosis. To date, 2 unrelated families with Majeed syndrome have been reported. Mutations in LPIN2 have been found in both families. Here we report a third consanguineous family with Majeed syndrome with a novel mutation. The patient, a 3-year-old Arabic girl, had hepatosplenomegaly and anemia as a neonate. At age 15 months, she developed recurrent episodes of fever and multifocal osteomyelitis. In addition, bone marrow aspiration demonstrated significant dyserythropoiesis, suggesting Majeed syndrome. Coding sequences and splice sites of LPIN2 were sequenced in the patient and her mother. A homozygous single-basepair change was detected in the donor splice site of exon 17 (c.2327+1G>C) in the patient; her mother was heterozygous at this site. These data confirm the role of LPIN2 mutations in the etiology of Majeed syndrome.

Autosomal dominant osteopetrosis: clinical severity and natural history of 94 subjects with a chloride channel 7 gene mutation

CONTEXT

Autosomal dominant osteopetrosis (ADO) is a sclerosing bone disorder caused by heterozygous mutations in the chloride channel 7 (ClCN7) gene. The clinical manifestations of this disease have not been well characterized since the discovery of the genetic basis of ADO.

OBJECTIVES

The primary objectives were to improve our understanding of ADO clinical characteristics and to study the natural history of the disease in the largest series of patients reported to date.

DESIGN AND SETTING

This study was primarily a retrospective cross-sectional analysis of individuals with a ClCN7 mutation that was conducted over a 4-yr period at a tertiary referral center and through family reunions. Longitudinal data on a subset of subjects were also studied.

PATIENTS AND INTERVENTIONS

We studied 311 subjects from 11 ADO families, including 62 individuals with ADO (patients with the classic clinical phenotype based on radiographs and/or biochemistry), 32 unaffected gene carriers (subjects with the gene mutation but no radiographic and/or biochemical phenotype), and 217 controls who did not harbor a ClCN7 gene mutation. Clinical data were collected through patient interviews and examinations, medical records, and/or self-reported responses on a questionnaire that was completed by all subjects.

MAIN OUTCOME MEASURES

The prevalence of fracture, osteomyelitis, visual loss, and bone marrow failure was determined. Differences in clinical manifestations were analyzed according to affected vs. carrier status, age, and underlying genotype.

RESULTS

Ninety-two percent of ADO subjects had at least one sequela of the disease. Gene carriers did not have an increased risk of disease manifestations, although they were found to have significant increases in bone mineral density (P < 0.05). Compared with controls, subjects with ADO had a significantly increased prevalence of fracture (84 vs. 36%; P < 0.0001) and osteomyelitis (16 vs. 0.9%; P < 0.0001). Severe fractures (defined as > or =10 fractures of any type and/or greater than one hip/femur fracture) were identified only in ADO subjects, and osteomyelitis typically occurred in the maxilla or mandible in older adults. Visual loss, which typically had its onset in childhood, and bone marrow failure occurred in 19 and 3% of ADO subjects, respectively. Adults were more likely to manifest an ADO clinical characteristic, but no definitive genotype-phenotype relationship could be concluded. Longitudinal data suggest that the ADO clinical phenotype worsens over time.

CONCLUSIONS

ADO caused by mutations in the CLCN7 gene is a frequently symptomatic disease manifested by a high rate of fracture, osteomyelitis, visual loss, and occasional bone marrow failure. The sequelae of ADO, which can be identified as early as infancy, appear to worsen over time. Fracture is the most prevalent consequence of ADO, although other more severe manifestations of disease can occur and should not be confused with recessive forms of osteopetrosis, particularly when identified in early childhood.

Serratia marcescens osteomyelitis in an infant

Neutrophil dysfunction can result from oxidative burst defect or from glucose-6-phosphate dehydrogenase (G6PD) deficiency; we noted both in the same patient. A 4-month-old male infant with G6PD deficiency presented with swelling of the left middle finger, left leg, and right big toe. At 5 weeks of age he was hospitalized for fever for 2 days. A maternal uncle died at 5 years of age and a male maternal cousin died at the age of 21 months, both reportedly diagnosed with chronic granulomatous disease (CGD). On physical examination, he had a swollen erythematous left third finger, left distal leg swelling, and right big toe abscess. None of these areas was significantly tender. WBC was 18.7 x 10(3)/mm(3) with 37% PMN and 5% bands. The x-ray films showed osteomyelitis in the left third proximal phalanx and the distal right first metatarsal. Culture from the toe abscess grew Serratia marcescens. His neutrophil oxidative burst was tested by the dihydrorhodamine-123 assay and was markedly suppressed, typical of CGD. The mother and maternal grandmother were found to be CGD carriers. He was treated with i.v. antibiotics for 4 weeks and was discharged on prophylactic trimethoprim, itraconazole and interferon gamma, with substantial reduction in infections. Infection in this infant was unusual in its nature, in affecting multiple sites, and in its causative organism. Immune deficiency was suspected, particularly of the phagocytic component, but could not be attributed to his moderate degree of primary G6PD deficiency. Additional immunologic evaluation and the family history led to the diagnosis of X-linked CGD.

Novel mutation in the interferon-gamma-receptor gene and susceptibility to mycobacterial infections

In 1981 we presented a patient with Mycobacterium intracellulare osteomyelitis and depressed monocyte cytotoxicity. It is now demonstrated that the molecular defect was a never-before-described nucleotide deletion at position 794 (794delT) in the interferon-gamma-receptor alpha-1 gene. The genetic defect was passed on to his daughter who was diagnosed with non-tuberculous mycobacterial osteomyelitis at the age of 7 years.

Homozygous mutations in LPIN2 are responsible for the syndrome of chronic recurrent multifocal osteomyelitis and congenital dyserythropoietic anaemia (Majeed syndrome)

BACKGROUND

Majeed syndrome is an autosomal recessive, autoinflammatory disorder characterised by chronic recurrent multifocal osteomyelitis and congenital dyserythropoietic anaemia. The objectives of this study were to map, identify, and characterise the Majeed syndrome causal gene and to speculate on its function and role in skin and bone inflammation.

METHODS

Six individuals with Majeed syndrome from two unrelated families were identified for this study. Homozygosity mapping and parametric linkage analysis were employed for the localisation of the gene responsible for Majeed syndrome. Direct sequencing was utilised for the identification of mutations within the genes contained in the region of linkage. Expression studies and in silico characterisation of the identified causal gene and its protein were carried out.

RESULTS

The phenotype of Majeed syndrome includes inflammation of the bone and skin, recurrent fevers, and dyserythropoietic anaemia. The clinical picture of the six affected individuals is briefly reviewed. The gene was mapped to a 5.5 cM interval (1.8 Mb) on chromosome 18p. Examination of genes in this interval led to the identification of homozygous mutations in LPIN2 in affected individuals from the two families. LPIN2 was found to be expressed in almost all tissues. The function of LPIN2 and its role in inflammation remains unknown.

CONCLUSIONS

We conclude that homozygous mutations in LPIN2 result in Majeed syndrome. Understanding the aberrant immune response in this condition will shed light on the aetiology of other inflammatory disorders of multifactorial aetiology including isolated chronic recurrent multifocal osteomyelitis, Sweet syndrome, and psoriasis.

Stress-induced colibacillosis and turkey osteomyelitis complex in turkeys selected for increased body weight

Two stress models were used to induce colibacillosis and turkey osteomyelitis complex (TOC): Escherichia coli challenge following dexamethasone injection (Dex) and E. coli challenge preceding transport stress (Transport). A total of 160 birds from 3 lines of turkeys: a slow-growing line selected for egg production (Egg), a line selected for 16-wk BW (F line), and a Commercial line (Comm), were studied in a 3 x 3 x 2 (line x treatment x sex) factorial design. At 14 wk, the Dex group was treated with 3 injections of 2 mg of Dex/kg of BW followed by airsac challenge with 100 cfu of E. coli. The Transport group was given 5,000 cfu of the same E. coli and 8 d later was transported for 3 h and held for an additional 9 h in the transport vehicle. Controls of each line were neither stressed nor challenged with E. coli. Birds were necropsied 2 wk postchallenge. All birds were sexed, scored for airsacculitis (AS) and TOC, and knee synovia were cultured for E. coli. Percent mortality was unaffected by sex, was increased by the Dex treatment, and was higher in Dex-treated male Comm-line birds and Dex-treated female F-line birds compared with their respective nonchallenged controls. Both treatments increased AS scores, and scores of Dex-treated male Comm-line birds and female F-line birds were also higher compared with their respective controls. Male Comm birds under Transport had higher AS scores as compared with nonchallenged males and challenged females. The TOC incidence was increased by Dex only. There was no TOC in Egg-line birds, whereas TOC incidence approached significance in both Comm and F lines compared with the Egg line (P = 0.06). Males had twice as much TOC as females, and this approached significance in the F line (P = 0.06). There was a low level of TOC in male Transport birds of both large-bodied lines, whereas no female Transport birds had TOC lesions. Dex-treated male birds of both the F line and Comm line had significantly higher incidence of TOC compared with their respective nonchallenged controls. The challenge strain of E. coli was isolated from more knee cultures of both large lines compared with the Egg line. Isolation was increased by Dex and was higher in male Comm-line birds and both male and female F-line birds relative to their controls. The difference in disease resistance between these lines suggests that selection for fast growth of turkeys may affect the stress response, resulting in increased chronic bacterial disease such as TOC.

The Toll-like receptor 4 (Asp299Gly) polymorphism is a risk factor for Gram-negative and haematogenous osteomyelitis

Osteomyelitis is a bone infection caused mostly by Staphylococcus aureus but also by Gram-negative bacteria. Toll-like receptors (TLRs), after recognizing microbial products, induce a signal in neutrophils, leading to NF-kappaB activation and transcription of pro-inflammatory genes. Polymorphisms in TLR2 (Arg753Gln) and TLR4 (Asp299Gly, Thr399Ile) genes are associated with bacterial infections, we therefore studied these polymorphisms in osteomyelitis patients. Homozygotes for the TLR4 (Asp299Gly) polymorphism were significantly more frequent among the 80 osteomyelitis patients than in the 155 healthy controls (3/80, 3.8%versus 0/155, 0%; P = 0.038). Carriers of one or two G alleles of this tlr4 polymorphism were more likely to have Gram-negative, haematogenous and/or chronic osteomyelitis than those without this mutation (P < 0.031). Patients with the TLR4 (Thr399Ile) mutant, which cosegregates with the TLR4 (Asp299Gly), were also carriers of this second polymorphism. No differences for the TLR2 (Arg753Gln) genotypes were found between patients and controls. Neutrophils of patients homozygous for the TLR4 (Asp299Gly) polymorphism showed lower LPS-induced apoptosis reduction, phosphorylation of the inhibitor of NF-kappaB, and lower IL-6 and TNF-alpha levels (P < 0.05). We report here for the first time an association between this TLR4 polymorphism and susceptibility to Gram-negative bacteria and haematogenous osteomyelitis.

Angiogenic gene therapy as a potential therapeutic agent in chronic osteomyelitis

Bacterial osteomyelitis is common, and outcomes are often poor. Standard therapies fail in 31% of cases, and lower extremity amputation and loss of independent functional status are common. Innovative therapies are desperately needed, particularly in diabetic patients with peripheral vascular disease at high risk for bad outcomes. Angiogenic gene therapy is a novel, logical and promising approach in these patients. Adult bone is not well vascularized. Host inflammation and bacterial toxin production result in further loss of vascularity, and produce bone necrosis. Dead bone acts as a foreign body, and is permissive for persistent infection. Poor blood supply prevents remodeling of dead bone, delivery of antibiotics, and phagocytosis of bacteria. Therefore, angiogenic gene therapy may be a useful therapeutic agent in osteomyelitis. It is reasonable to pursue studies of angiogenic agents in established animal models of chronic osteomyelitis, not only with vascular endothelial growth factor (VEGF), but also with the powerful bone angiogenic agent, placental growth factor, as well as other agents with tissue regenerative and angiogenic potential, such as sonic hedgehog, bone morphogenetic proteins, matrix metalloproteinase-9, secretoneurin, and perhaps pluripotent stem cells. If successful, animal studies could lead to pilot studies of one or more of these agents as adjunctive therapy, in addition to antibiotics, in diabetic patients with chronic osteomyelitis who have failed conventional treatment.

A missense mutation in pstpip2 is associated with the murine autoinflammatory disorder chronic multifocal osteomyelitis

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disorder that primarily affects bone but is often accompanied by inflammation of the skin and/or gastrointestinal tract. The etiology is unknown but evidence suggests a genetic component to disease susceptibility. Although most cases of CRMO are sporadic, there is an autosomal recessive syndromic form of the disease, called Majeed syndrome, which is due to homozygous mutations in LPIN2. In addition, there is a phenotypically similar mouse, called cmo (chronic multifocal osteomyelitis) in which the disease is inherited as an autosomal recessive disorder. The cmo locus has been mapped to murine chromosome 18. In this report, we describe phenotypic abnormalities in the cmo mouse that include bone, cartilage and skin inflammation. Utilizing a backcross breeding strategy, we refined the cmo locus to a 1.3 Mb region on murine chromosome 18. Within the refined region was the gene pstpip2, which shares significant sequence homology to the PSTPIP1. Mutations in PSTPIP1 have been shown to cause the autoinflammatory disorder PAPA syndrome (pyogenic arthritis, pyoderma gangrenosum and acne). Mutation analysis, utilizing direct sequencing, revealed a single base pair change c.293T --> C in the pstpip2 gene resulting in a highly conserved leucine at amino acid 98 being replaced by a proline (L98P). No other mutations were found in the coding sequence of the remaining genes in the refined interval, although a 50 kb gap remains unexplored. These data suggest that mutations in pstpip2 may be the genetic explanation for the autoinflammatory phenotype seen in the cmo mouse.

A novel mutation in IFN-gamma receptor 2 with dominant negative activity: biological consequences of homozygous and heterozygous states

We identified two siblings homozygous for a single base pair deletion in the IFN-gammaR2 transmembrane domain (791delG) who presented with multifocal Mycobacterium abscessus osteomyelitis (patient 1) and disseminated CMV and Mycobacterium avium complex infection (patient 2), respectively. Although the patients showed no IFN-gammaR activity, their healthy heterozygous parents showed only partial IFN-gammaR activity. An HLA-identical bone marrow transplant from the mother led patient 1 to complete hemopoietic reconstitution, but only partial IFN-gammaR function. We cloned and expressed fluorescent fusion proteins of the wild-type IFN-gammaR2, an IFN-gammaR2 mutant previously described to produce a complete autosomal recessive deficiency (278del2), and of 791delG to determine whether the intermediate phenotype in the 791delG heterozygous state was caused by haploinsufficiency or a dominant negative effect. When cotransfected together with the wild-type vector into IFN-gammaR2-deficient fibroblasts, the fusion protein with 791delG inhibited IFN-gammaR function by 48.7 +/- 5%, whereas fusion proteins with 278del2 had no inhibitory effect. Confocal microscopy of 791delG fusion proteins showed aberrant diffuse intracellular accumulation without plasma membrane localization. The fusion protein created by 791delG did not complete Golgi processing, and was neither expressed on the plasma membrane, nor shed extracellularly. The mutant construct 791delG exerts dominant negative effects on IFN-gamma signaling without cell surface display, suggesting that it is acting on pathways other than those involved in cell surface recognition of ligand.