Pigmentary hypertrichosis and non-autoimmune insulin-dependent diabetes mellitus (PHID) syndrome is associated with severe chronic inflammation and cardiomyopathy, and represents a new monogenic autoinflammatory syndrome

Combination of four features of SLC29A3 spectrum disorder in a child: A case report

SLC29A3 spectrum disorder, also known as histiocytosis-lymphadenopathy plus syndrome (HLPS), presents a wide variety of multi-systemic manifestations that can be mistaken for other conditions. Herein, we report a 9-year-old girl who presented with a complex clinical presentation since birth, including chronic generalized lymphadenopathy in association with hepatosplenomegaly, short stature, flexion contractures, hearing loss, hyperpigmentation, and heart anomalies. She was ultimately diagnosed with the SLC29A3 spectrum disorder.

Solute Carrier Nucleoside Transporters in Hematopoiesis and Hematological Drug Toxicities: A Perspective

Simple Summary

Anticancer nucleoside analogs are promising treatments that often result in damaging toxicities and therefore ineffective treatment. Mechanisms of this are not well-researched, but cellular nucleoside transport research in mice might provide additional insight given transport’s role in mammalian hematopoiesis. Cellular nucleoside transport is a notable component of mammalian hematopoiesis due to how mutations within it relate to hematological abnormities. This review encompasses nucleoside transporters, focusing on their inherent properties, hematopoietic role, and their interplay in nucleoside drug treatment side effects. We then propose potential mechanisms to explain nucleoside transport involvement in blood disorders. Finally, we point out and advocate for future research areas that would improve therapeutic outcomes for patients taking nucleoside analog therapies.

Abstract

Anticancer nucleoside analogs produce adverse, and at times, dose-limiting hematological toxicities that can compromise treatment efficacy, yet the mechanisms of such toxicities are poorly understood. Recently, cellular nucleoside transport has been implicated in normal blood cell formation with studies from nucleoside transporter-deficient mice providing additional insights into the regulation of mammalian hematopoiesis. Furthermore, several idiopathic human genetic disorders have revealed nucleoside transport as an important component of mammalian hematopoiesis because mutations in individual nucleoside transporter genes are linked to various hematological abnormalities, including anemia. Here, we review recent developments in nucleoside transporters, including their transport characteristics, their role in the regulation of hematopoiesis, and their potential involvement in the occurrence of adverse hematological side effects due to nucleoside drug treatment. Furthermore, we discuss the putative mechanisms by which aberrant nucleoside transport may contribute to hematological abnormalities and identify the knowledge gaps where future research may positively impact treatment outcomes for patients undergoing various nucleoside analog therapies.

Genetics of lipodystrophy syndromes

Lipodystrophic syndromes (LS) constitute a clinically and genetically heterogeneous group of diseases characterized by a loss of adipose tissue. These syndromes are usually associated with metabolic complications, which are determinant for morbidity and mortality. The classical forms of LS include partial, generalized, and progeroid lipodystrophies. They are usually due to defects in proteins playing a key role in adipogenesis and adipocyte functions. More recently, systemic disorders combining lipodystrophy and multiple organ dysfunction have been described, including autoinflammatory syndromes, mitochondrial disorders, as well as other complex entities. To date, more than thirty genes have been implicated in the monogenic forms of LS, but the majority of them remain genetically-unexplained. The associated pathophysiological mechanisms also remain to be clarified in many instances. Next generation sequencing-based approaches allow simultaneous testing of multiple genes and have become crucial to speed up the identification of new disease-causing genes. The challenge for geneticists is now the interpretation of the amount of available genetic data, generated especially by exome and whole-genome sequencing. International recommendations on the interpretation and classification of variants have been set up and are regularly reassessed. Very close collaboration between geneticists, clinicians, and researchers will be necessary to make rapid progress in understanding the molecular and cellular basis of these diseases, and to promote personalized medicine.

H syndrome: A review of treatment options and a hypothesis of phenotypic variability

H syndrome is a rare autosomal recessive disorder with clinical features comprising: hyperpigmentation, hypertrichosis, hearing loss, heart anomalies, low height, hypogonadism and hepatosplenomegaly. H syndrome results from loss-of-function mutations in SLC29A3 which leads to abnormal proliferation and function of histiocytes. Herein, we discuss the considerable phenotypic heterogeneity detected in a consanguineous Egyptian family comprising of four affected siblings, two of which are monozygotic twin and the possible therapeutics. The phenotypic variability may be attributed to the role of histiocytes in the tissue response to injury. Such variable expressivity of H syndrome renders the diagnosis challenging and delays the management. The different treatment approaches used for this rare entity are reviewed.

Patient with H syndrome, cardiogenic shock, multiorgan infiltration, and digital ischemia

BACKGROUND

H syndrome (HS) is a rare autoinflammatory disease caused by a mutation in the solute carrier family 29, member 3 (SCL29A3) gene. It has a variable clinical presentation and little phenotype-genotype correlation. The pathognomonic sign of HS is cutaneous hyperpigmentation located mainly in the inner thighs and often accompanied by other systemic manifestations. Improvement after tocilizumab treatment has been reported in a few patients with HS. We report the first patient with HS who presented cardiogenic shock, multiorgan infiltration, and digital ischemia.

CASE PRESENTATION

8-year-old boy born to consanguineous parents of Moroccan origin who was admitted to the intensive care unit during the Coronavirus Disease-2019 (COVID-19) pandemic with tachypnoea, tachycardia, and oliguria. Echocardiography showed dilated cardiomyopathy and severe systolic dysfunction compatible with cardiogenic shock. Additionally, he presented with multiple organ dysfunction syndrome. SARS-CoV-2 polymerase chain reaction (PCR) and antibody detection by chromatographic immunoassay were negative. A previously ordered gene panel for pre-existing sensorineural hearing loss showed a pathological mutation in the SCL29A3 gene compatible with H syndrome. Computed tomography scan revealed extensive alveolar infiltrates in the lungs and multiple poor defined hypodense lesions in liver, spleen, and kidneys; adenopathy; and cardiomegaly with left ventricle subendocardial nodules. Invasive mechanical ventilation, broad antibiotic and antifungal coverage showed no significant response. Therefore, Tocilizumab as compassionate use together with pulsed intravenous methylprednisolone was initiated. Improvement was impressive leading to normalization of inflammation markers, liver and kidney function, and stabilising heart function. Two weeks later, he was discharged and has been clinically well since then on two weekly administration of Tocilizumab.

CONCLUSIONS

We report the most severe disease course produced by HS described so far in the literature. Our patient's manifestations included uncommon, new complications such as acute heart failure with severe systolic dysfunction, multi-organ cell infiltrate, and digital ischemia. Most of the clinical symptoms of our patient could have been explained by SARS-CoV-2, demonstrating the importance of a detailed differential diagnosis to ensure optimal treatment. Although the mechanism of autoinflammation of HS remains uncertain, the good response of our patient to Tocilizumab makes a case for the important role of IL-6 in this syndrome and for considering Tocilizumab as a first-line treatment, at least in severely affected patients.

Identification of Critical Transcriptomic Signaling Pathways in Patients with H Syndrome and Rosai-Dorfman Disease

Biallelic mutations in SLC29A3 cause histiocytosis-lymphadenopathy plus syndrome, also known as H syndrome (HS). HS is a complex disorder, with ~ 25% of patients developing autoinflammatory complications consisting of unexplained fevers, persistently elevated inflammatory markers, and unusual lymphadenopathies, with infiltrating CD68⁺, S100⁺, and CD1a^- histiocytes, resembling the immunophenotype found in Rosai-Dorfman disease (RDD). We investigated the transcriptomic profiles of monocytes, non-activated (M0), classically activated (M1), and alternatively activated macrophages (M2) in two patients with HS, one without autoinflammatory (HS1) and one with autoinflammatory complications (HS2). RNA sequencing revealed a dysregulated transcriptomic profile in both HS patients compared to healthy controls (HC). HS2, when compared to HS1, had several differentially expressed genes, including genes associated with lymphocytic-histiocytic predominance (e.g. NINL) and chronic immune activation (e.g. B2M). The transcriptomic and cytokine profiles of HS patients were comparable to patients with SAID with high levels of TNF. SERPINA1 gene expression was found to be upregulated in all patients studied. Moreover, higher levels of IFNγ were found in the serum of both HS patients when compared to HC. Gene ontology (GO) enrichment analysis of the DEGs in HS patients revealed the terms "type I IFN," "IFNγ signaling pathway," and "immune responses" as the top 3 most significant terms for monocytes. Gene expression analysis of lymph node biopsies from sporadic and H syndrome-associated RDD suggests common underlying pathological process. In conclusion, monocytes and macrophages from both HS patients showed transcriptomic profiles similar to SAIDs and also uniquely upregulated IFNγ signature. These findings may help find better therapeutic options for this rare disorder.

Overview of Atypical Diabetes

Although type 1 diabetes mellitus and, to a lesser extent, type 2 diabetes mellitus, are the prevailing forms of diabetes in youth, atypical forms of diabetes are not uncommon and may require etiology-specific therapies. By some estimates, up to 6.5% of children with diabetes have monogenic forms. Mitochondrial diabetes and cystic fibrosis related diabetes are less common but often noted in the underlying disease. Atypical diabetes should be considered in patients with a known disorder associated with diabetes, aged less than 25 years with nonautoimmune diabetes and without typical characteristics of type 2 diabetes mellitus, and/or with comorbidities associated with atypical diabetes.

Mycophenolate mofetil treatment of an H syndrome patient with a SLC29A3 mutation

H syndrome is a complex multi-organ disorder with autosomal recessive inheritance. The skin manifestations include early onset hyperpigmentation and hypertrichosis, followed by skin induration often diagnosed as scleromyxedema and morphea. There is no effective treatment. Our objective was to study the efficacy of mycophenolate mofetil in a patient with genetically confirmed H syndrome. We sought the genetic cause of H syndrome with whole-exome sequencing (WES) of the proband. Genome-wide homozygosity mapping (HM) provided additional evidence for causality of the variant suggested by WES. Here, we report a patient with characteristic clinical features of H syndrome, and the diagnosis was confirmed by identification of a homozygous SLC29A3 mutation (p.Gly437Arg). The patient was initially treated with prednisolone and cyclosporine, but after development of side-effects she was placed on mycophenolate mofetil. After the treatment with mycophenolate mofetil was initiated, resolution of hyperpigmentation was noted, and no new lesions developed during an 18-month follow-up period. Thus, mycophenolate mofetil could be considered as a safe and partially effective treatment of H syndrome.

A case of Myhre syndrome mimicking juvenile scleroderma

BACKGROUND

Myhre syndrome is a genetic disorder caused by gain of function mutations in the SMAD Family Member 4 (SMAD4) gene, resulting in progressive, proliferative skin and organ fibrosis. Skin thickening and joint contractures are often the main presenting features of the disease and may be mistaken for juvenile scleroderma.

CASE PRESENTATION

We report a case of a 13 year-old female presenting with widespread skin thickening and joint contractures from infancy. She was diagnosed with diffuse cutaneous systemic sclerosis, and treatment with corticosteroids and subcutaneous methotrexate recommended. There was however disease progression prompting genetic testing. This identified a rare heterozygous pathogenic variant c.1499 T > C (p.Ile500Thr) in the SMAD4 gene, suggesting a diagnosis of Myhre syndrome. Securing a molecular diagnosis in this case allowed the cessation of immunosuppression, thus reducing the burden of unnecessary and potentially harmful treatment, and allowing genetic counselling.

CONCLUSION

Myhre Syndrome is a rare genetic mimic of scleroderma that should be considered alongside several other monogenic diseases presenting with pathological fibrosis from early in life. We highlight this case to provide an overview of these genetic mimics of scleroderma, and highlight the molecular pathways that can lead to pathological fibrosis. This may provide clues to the pathogenesis of sporadic juvenile scleroderma, and could suggest novel therapeutic targets.

Mutation in the SLC29A3 Gene in an Egyptian Patient with H Syndrome: A Case Report and Review of Literature

Histiocytosis-lymphadenopathy plus syndrome (H syndrome) is caused by mutations in the SLC29A3 gene that result in histiocytic infiltration of numerous organs. Patients suffering from this disorder can be easily mistaken for similar conditions such as Muckle-Wells syndrome. We present a 9.5-year-old boy, who is the offspring of a consanguineous marriage. He suffered from sensorineural hearing loss, dark hyperpigmented indurated dry areas on the medial thighs sparing the knees with hypertrichosis on the affected areas, and areas of hypopigmentation on the abdomen. The patient displayed mild dysmorphism including frontal bossing, synophrys, bilateral proptosis (with normal thyroid function), thick eyebrows, flat nose, long philtrum, and pectus excavatum. Formal intelligence testing showed that he was a slow learner. Laboratory findings included elevated serum amyloid-A, erythrocyte sedimentation rate, and total proteins in urine tests. Complete blood count showed mild microcytic hypochromic anemia. The molecular analysis was crucial to confirm the provisional clinical diagnosis. H syndrome is a rare autoinflammatory syndrome with pleiotropic manifestations that affect many organs and can be mistaken for other conditions. Our patient's description may expand the phenotype of H syndrome, as areas of hypopigmentation were observed on the abdomen. Molecular analysis of SLC29A3 -related diseases is essential to highlight the variability and increase the awareness of H syndrome aiming for early diagnosis and proper treatment.

A novel 3' untranslated region mutation in the SLC29A3 gene associated with pigmentary hypertrichosis and non-autoimmune insulin-dependent diabetes mellitus syndrome

BACKGROUND

Pigmentary hypertrichosis and non-autoimmune insulin-dependent diabetes mellitus (PHID) is one of the rare H syndrome diseases mainly characterized by hyperpigmentation, hypertrichosis, sensorineural hearing loss, cardiac complications, developmental delay, and diabetes mellitus (DM). Mutations in the coding regions of the SLC29A3 gene that encodes for an equilibrative nucleoside transporter (ENT3) have been reported to cause the phenotypic spectrum of the H syndrome. Disease-causing mutations in the untranslated regions (UTRs) of the SLC29A3 gene have not been previously described in the literature. The aim of the study is to describe and assess the pathogenicity of a novel 3'UTR mutation in the SLC29A3 gene associated with the PHID phenotype in two Turkish patients.

METHODS

The mutation was identified by a targeted gene approach. To understand the pathogenicity of this 3'UTR mutation, RNA and protein expression studies were performed by using the quantitative real-time polymerase chain reaction method and western blotting, respectively, using fibroblasts cultured from the patients' skin biopsies.

RESULTS

SLC29A3 and ENT3 expression levels were both decreased in the patients compared to controls matched for passage numbers, RNA, and protein extraction methods.

CONCLUSIONS

A novel 3'UTR mutation in the SLC29A3 gene is associated with the PHID syndrome, highlighting a potentially new pathological mechanism for this disease. The involvement of the 3'UTR has not been previously established in any of the H syndrome disease cluster or in any complex syndrome of DM.

Off-label use of tocilizumab to treat non-juvenile idiopathic arthritis in pediatric rheumatic patients: a literature review

Tocilizumab, an anti-interleukin-6 (IL-6) agent, is indicated as a treatment for several autoimmune or inflammatory diseases, including rheumatoid arthritis and juvenile idiopathic arthritis (JIA). IL-6 plays roles in both immune system dysregulation and inflammation, and thus efforts to extend the utility of tocilizumab in patients with autoinflammatory conditions are ongoing. Here, we survey the literature on the off-label use of tocilizumab in patients with juvenile-onset rheumatic diseases including juvenile systemic lupus erythematosus (SLE), juvenile dermatomyositis (DM), vasculitis, juvenile scleroderma, and other autoinflammatory diseases. There is no real evidence that tocilizumab is useful for patients with SLE and juvenile DM, but several cases of childhood Takayasu arteritis have experienced promising outcomes. In juvenile-onset scleroderma, for which no therapy that can halt disease progression is available, tocilizumab may stop progression and the associated functional impairment. Tocilizumab prevents systemic inflammation in patients with Kawasaki's disease, but may develop coronary aneurysms. Tocilizumab has been used to treat several pediatric autoinflammatory diseases, including JIA-associated uveitis and Castleman's disease. Further work in larger populations is necessary to confirm the effects of tocilizumab in patients with pediatric rheumatic diseases.

H syndrome: 5 new cases from the United States with novel features and responses to therapy

BACKGROUND

H Syndrome is an autosomal recessive disorder characterized by cutaneous hyperpigmentation, hypertrichosis, and induration with numerous systemic manifestations. The syndrome is caused by mutations in SLC29A3, a gene located on chromosome 10q23, which encodes the human equilibrative transporter 3 (hENT3). Less than 100 patients with H syndrome have been described in the literature, with the majority being of Arab descent, and only a few from North America.

CASE PRESENTATION

Here we report five pediatric patients from three medical centers in the United States who were identified to have H syndrome by whole exome sequencing. These five patients, all of whom presented to pediatric rheumatologists prior to diagnosis, include two of Northern European descent, bringing the total number of Caucasian patients described to three. The patients share many of the characteristics previously reported with H syndrome, including hyperpigmentation, hypertrichosis, short stature, insulin-dependent diabetes, arthritis and systemic inflammation, as well as some novel features, including selective IgG subclass deficiency and autoimmune hepatitis. They share genetic mutations previously described in patients of the same ethnic background, as well as a novel mutation. In two patients, treatment with prednisone improved inflammation, however both patients flared once prednisone was tapered. In one of these patients, treatment with tocilizumab alone resulted in marked improvement in systemic inflammation and growth. The other had partial response to prednisone, azathioprine, and TNF inhibition; thus, his anti-TNF biologic was recently switched to tocilizumab due to persistent polyarthritis. Another patient improved on Methotrexate, with further improvement after the addition of tocilizumab.

CONCLUSION

H syndrome is a rare autoinflammatory syndrome with pleiotropic manifestations that affect multiple organ systems and is often mistaken for other conditions. Rheumatologists should be aware of this syndrome and its association with arthritis. It should be considered in patients with short stature and systemic inflammation, particularly with cutaneous findings. Some patients respond to treatment with biologics alone or in combination with other immune suppressants; in particular, treatment of systemic inflammation with IL-6 blockade appears to be promising. Overall, better identification and understanding of the pathophysiology may help devise earlier diagnosis and better treatment strategies.

Untangling the web of systemic autoinflammatory diseases

The innate immune system is involved in the pathophysiology of systemic autoinflammatory diseases (SAIDs), an enlarging group of disorders caused by dysregulated production of proinflammatory cytokines, such as interleukin-1β and tumor necrosis factor-α, in which autoreactive T-lymphocytes and autoantibodies are indeed absent. A widely deranged innate immunity leads to overactivity of proinflammatory cytokines and subsequent multisite inflammatory symptoms depicting various conditions, such as hereditary periodic fevers, granulomatous disorders, and pyogenic diseases, collectively described in this review. Further research should enhance our understanding of the genetics behind SAIDs, unearth triggers of inflammatory attacks, and result in improvement for their diagnosis and treatment.

The expanding spectrum of rare monogenic autoinflammatory diseases

Monogenic autoinflammatory diseases are a group of hereditary disorders characterized by a clinical and biological inflammatory syndrome in which there is little or no evidence of autoimmunity. The discovery of the first causative gene in 1997 was rapidly followed by the identification of many others from the same group. The mutated proteins can be directly or indirectly involved in the regulation of inflammation. The available literature includes numerous reviews, which address the principle diseases, but we wanted to focus on the most recent rare syndromes. A comprehensive review is thus provided, including taxonomic, genetic, and epidemiological data, along with characteristics defining positive and differential diagnoses and treatment. We believe that this update will assist physicians in correctly naming their patient’s illness. This is an essential step for the effective and targeted management of an orphan disease.