Immune Dysregulation Mimicking Systemic Lupus Erythematosus in a Patient With Lysinuric Protein Intolerance: Case Report and Review of the Literature

LASSO-derived nomogram for early identification of pediatric monogenic lupus

BACKGROUND

Monogenic lupus is defined as systemic lupus erythematosus (SLE)/SLE-like patients with either dominantly or recessively inherited pathogenic variants in a single gene with high penetrance. However, because the clinical phenotype of monogenic SLE is extensive and overlaps with that of classical SLE, it causes a delay in diagnosis and treatment. Currently, there is a lack of early identification models for clinical practitioners to provide early clues for recognition. Our goal was to create a clinical model for the early identification of pediatric monogenic lupus, thereby facilitating early and precise diagnosis and treatment for patients.

METHODS

This retrospective cohort study consisted of 41 cases of monogenic lupus treated at the Department of Pediatrics at Peking Union Medical College Hospital from June 2012 to December 2022. The control group consisted of classical SLE patients recruited at a 1:2 ratio. Patients were randomly divided into a training group and a validation group at a 7:3 ratio. A logistic regression model was established based on the least absolute shrinkage and selection operator to generate the coefficient plot. The predictive ability of the model was evaluated using receiver operator characteristic curves and the area under the curve (AUC) index.

RESULTS

A total of 41 cases of monogenic lupus patients and 82 cases of classical SLE patients were included. Among the monogenic lupus cases (with a male-to-female ratio of 1:1.05 and ages of onset ranging from birth to 15 years), a total of 18 gene mutations were identified. The variables included in the coefficient plot were age of onset, recurrent infections, intracranial calcifications, growth and developmental delay, abnormal muscle tone, lymphadenopathy/hepatosplenomegaly, and chilblain-like skin rash. Our model demonstrated satisfactory diagnostic performance through internal validation, with an AUC value of 0.97 (95% confidence interval = 0.92-0.97).

CONCLUSIONS

We summarized and analyzed the clinical characteristics of pediatric monogenic lupus and developed a predictive model for early identification by clinicians. Clinicians should exercise high vigilance for monogenic lupus when the score exceeds - 9.032299.

Lysinuric protein intolerance with novel mutations in solute carrier family 7A member 7 in a Chinese family

Introduction

Lysinuric protein intolerance (LPI) is a rare genetic disorder caused by mutations in the solute carrier family 7A member 7 (SLC7A7) gene.

Case presentation

We presented two siblings with LPI, carrying novel mutations of c.776delT (p.L259Rfs*18) and c.155G>T (p.G52V) in SLC7A7. The younger sibling, preferring protein-rich foods, showed severe symptoms, including alveolar proteinosis, macrophage activation syndrome, severe diarrhea, and disturbance of consciousness with involuntary movements. In contrast, the elder sibling only had mild symptoms, likely due to aversion to protein-rich food since toddler age.

Conclusion

LPI is a congenital genetic metabolic disease with multi-system involvement. Initiating appropriate protein-restricted diet therapy as soon as possible could help prevent the progression of LPI.

The Great Masquerade: Varying Manifestations of Lysinuric Protein Intolerance

Lysinuric protein intolerance (LPI) is an inborn metabolic error caused by cationic amino acid transport defects. The disease has a significant degree of phenotypic variation, with no confirmed genotype-phenotype correlation. Because it presents with symptoms similar to far more common diseases, the diagnosis is often missed, resulting in increased morbidity and mortality. This case series describes three examples of LPI with pulmonary, neurological, and immunological manifestations, emphasising the importance of keeping this disorder on the differential list. Appropriate metabolic and genetic testing is important in providing the correct diagnosis and timely care in such cases.

A novel variant in a Chinese boy with lysinuric protein intolerance: A case report and literature review

We report a case of a 4-year-old boy with lysinuric protein intolerance in China. The patient presented with interstitial lung disease with obvious clubbing of the fingers and toes. During the course of diagnosis and treatment, we found he was averse to a high-protein diet, intolerant to activity, and had a history of diarrhea and fractures. Physical examination revealed hepatosplenomegaly and clubbing of the fingers and toes. Next-generation sequencing revealed compound heterozygous mutations (c.1387delG, c.958T > C) in SLC7A7, which was confirmed as a disease-causing gene for lysinuric protein intolerance. After a literature review, we found that c.958T > C had not been previously reported, and summarized the clinical and genetic characteristics of patients from different continents. His symptoms improved significantly after 3 months of being on a low-protein diet, supplementation with lysine, citrulline, carnitine, and trace elements, and oral corticosteroid treatment for 2 months. The patient is still under follow-up.

[Enteral nutrition support for lysinuric protein intolerance: a case report and literature review]

OBJECTIVES

To summarize the clinical characteristics and nutrition therapy for children with lysinuric protein intolerance (LPI).

METHODS

The clinical manifestations, laboratory test results and enteral nutrition treatment in a girl with LPI diagnosed in Xiangya Hospital, Central South University were retrospective analyzed. Additionally, the data of the children with LPI reported in China and overseas were reviewed.

RESULTS

A case of 4-year-old girl was presented, who exhibited significant gastrointestinal symptoms, such as chronic abdominal distension, prolonged diarrhea, recurrent pneumonia, and limited growth. She had a poor response to anti-infection treatment. After receiving enteral nutrition therapy, she did not experience any gastrointestinal discomfort, and there were improvements in the levels of hemoglobin, albumin, and blood ammonia. Unfortunately, due to serious illness, she declined further treatment and later passed away. A total of 92 cases of pediatric patients with LPI have been reported to date, including one case reported in this study. Most children with LPI experienced disease onset after weaning or introduction of complementary foods, presenting with severe digestive system symptoms, malnutrition, and growth retardation. It is noteworthy that only 50% (46/92) of these cases received nutritional therapy, which effectively improved their nutritional status. Among the 92 children, 8 (9%) died, and long-term follow-up data were lacking in other reports.

CONCLUSIONS

LPI often involves the digestive system and may result in growth restriction with a poor prognosis. Nutritional therapy plays a crucial role in the comprehensive treatment of LPI.

Lysinuric protein intolerance caused by a homozygous SLC7A7 deletion and presented with hyperferritinemia and osteoporosis in two siblings

Lysinuric protein intolerance (LPI) is a rare, inherited aminoaciduria caused by biallelic pathogenic variants in the amino acid transporter gene SLC7A7 (OMIM *603593). Individuals with LPI show extreme variability in their clinical presentation, and LPI is included in the differential diagnosis of several disorders such as urea cycle disorders, lysosomal storage diseases, malabsorption diseases, autoimmune disorders, hemochromatosis, and osteoporosis. The phenotypic variability of LPI and the lack of a specific clinical presentation have caused various misdiagnoses. Here, we report two siblings diagnosed in their 4th decade of life with LPI, manifesting rare hyperferritinemia. Additionally, they presented with short stature, multiple bone fractures due to osteoporosis, and they showed an aversion to protein-rich food. Using a combination of exome sequencing, microarray analysis and qPCR, we identified a novel homozygous deletion in SLC7A7 encompassing exons 3 to 10, which is predicted to lead to disruption of SLC7A7 function. This is the first report of lysinuric protein intolerance in a Turkish family associated with this so far unknown deletion in SLC7A7.

Inborn errors of amino acid metabolism - from underlying pathophysiology to therapeutic advances

Amino acids are organic molecules that serve as basic substrates for protein synthesis and have additional key roles in a diverse array of cellular functions, including cell signaling, gene expression, energy production and molecular biosynthesis. Genetic defects in the synthesis, catabolism or transport of amino acids underlie a diverse class of diseases known as inborn errors of amino acid metabolism. Individually, these disorders are rare, but collectively, they represent an important group of potentially treatable disorders. In this Clinical Puzzle, we discuss the pathophysiology, clinical features and management of three disorders that showcase the diverse clinical presentations of disorders of amino acid metabolism: phenylketonuria, lysinuric protein intolerance and homocystinuria due to cystathionine β-synthase (CBS) deficiency. Understanding the biochemical perturbations caused by defects in amino acid metabolism will contribute to ongoing development of diagnostic and management strategies aimed at improving the morbidity and mortality associated with this diverse group of disorders.

Delayed skeletal development and IGF-1 deficiency in a mouse model of lysinuric protein intolerance

SLC7A7 deficiency, or lysinuric protein intolerance (LPI), causes loss of function of the y+LAT1 transporter critical for efflux of arginine, lysine and ornithine in certain cells. LPI is characterized by urea cycle dysfunction, renal disease, immune dysregulation, growth failure, delayed bone age and osteoporosis. We previously reported that Slc7a7 knockout mice (C57BL/6×129/SvEv F2) recapitulate LPI phenotypes, including growth failure. Our main objective in this study was to characterize the skeletal phenotype in these mice. Compared to wild-type littermates, juvenile Slc7a7 knockout mice demonstrated 70% lower body weights, 87% lower plasma IGF-1 concentrations and delayed skeletal development. Because poor survival prevents evaluation of mature knockout mice, we generated a conditional Slc7a7 deletion in mature osteoblasts or mesenchymal cells of the osteo-chondroprogenitor lineage, but no differences in bone architecture were observed. Overall, global Slc7a7 deficiency caused growth failure with low plasma IGF-1 concentrations and delayed skeletal development, but Slc7a7 deficiency in the osteoblastic lineage was not a major contributor to these phenotypes. Future studies utilizing additional tissue-specific Slc7a7 knockout models may help dissect cell-autonomous and non-cell-autonomous mechanisms underlying phenotypes in LPI.

Characteristics and genetic analysis of patients suspected with early-onset systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is rarely diagnosed before 5-years-old. Those with disease onset at a very young age are predicted by a higher genetic risk and a more severe phenotype. We performed whole-exome sequencing to survey the genetic etiologies and clinical manifestations in patients fulfilling 2012 SLICC SLE classification criteria before the age of 5.

CASE PRESENTATION

Among the 184 childhood-onset SLE patients regularly followed in a tertiary medical center in Taiwan, 7 cases (3.8%) of which onset ≦ 5 years of age were identified for characteristic review and genetic analysis. Compared to those onset at elder age, cases onset before the age of 5 are more likely to suffer from proliferative glomerulonephritis, renal thrombotic microangiopathy, neuropsychiatric disorder and failure to thrive. Causative genetic etiologies were identified in 3. In addition to the abundance of autoantibodies, patient with homozygous TREX1 (c.292_293 ins A) mutation presented with chilblain-like skin lesions, peripheral spasticity, endocrinopathy and experienced multiple invasive infections. Patient with SLC7A7 (c.625 + 1 G > A) mutation suffered from profound glomerulonephritis with full-house glomerular deposits as well as hyperammonemia, metabolic acidosis and episodic conscious disturbance. Two other cases harbored variants in lupus associating genes C1s, C2, DNASE1 and DNASE1L3 and another with CFHR4. Despite fulfilling the classification criteria for lupus, many of the patients required treatments beyond conventional therapy.

CONCLUSIONS

Genetic etiologies and lupus mimickers were found among a substantial proportion of patients suspected with early-onset SLE. Detail clinical evaluation and genetic testing are important for tailored care and personalized treatment.

Systemic Lupus Erythematosus and Hereditary Coproporphyria: Two Different Entities Diagnosed by WES in the Same Patient

Background

Hereditary coproporphyria (HCP) is a rare autosomal dominant disorder caused by a partial deficiency of coproporphyrinogen III oxidase (CPOX), and systemic lupus erythematosus (SLE) is an autoimmune disease with a strong genetic predisposition. SLC7A7 (solute carrier family 7 member 7) may be associated with monogenic lupus disease; however, only 2 cases of concomitant HCP and SLE have been reported.

Methods

We report a 30-year-old woman with a six-year history of SLE presenting with abdominal pain, vomiting, dysuria, tachycardia, and hyponatremia. Whole exome sequencing (WES) and Sanger sequencing were carried out for the proband and members of her pedigree to detect the genetic background. The Gene Expression Omnibus (GEO) database was used to search the related gene expression profiles. Differentially expressed genes (DEGs) were identified using GEO2R.

Result

A novel heterozygous splicing mutation of CPOX (NM_000097): c.700+2 T > C (intron 2) was detected by WES in the proband, and it was considered likely pathogenic (PSV1+PM2). Sanger sequencing verified the heterozygous mutation of CPOX in the proband, although it was not detected in her father. WES also identified 62 other gene variants, especially two heterozygous variants in SLC7A7 (NM_001126106): c.250G > A (p. V84I) and c.625+1G > A (splicing). DEGs were detected from GSE51997, and the expression of CPOX was downregulated in SLE patients compared with normal controls (adj. P = 0.0071, logFC = −1.0975).

Conclusion

This study presents the first reported case of SLE coexisting with HCP in China; moreover, a novel splicing mutation of CPOX, i.e., c.700+2 T > C (intron 2), and two heterozygous mutations of SLC7A7 were reported. The simultaneous mutations of CPOX and SLC7A7 may explain the etiopathogenetic connections of HCP and SLE.

Centers for Mendelian Genomics: A decade of facilitating gene discovery

PURPOSE

Mendelian disease genomic research has undergone a massive transformation over the past decade. With increasing availability of exome and genome sequencing, the role of Mendelian research has expanded beyond data collection, sequencing, and analysis to worldwide data sharing and collaboration.

METHODS

Over the past 10 years, the National Institutes of Health-supported Centers for Mendelian Genomics (CMGs) have played a major role in this research and clinical evolution.

RESULTS

We highlight the cumulative gene discoveries facilitated by the program, biomedical research leveraged by the approach, and the larger impact on the research community. Beyond generating a list of gene-phenotype relationships and participating in widespread data sharing, the CMGs have created resources, tools, and training for the larger community to foster understanding of genes and genome variation. The CMGs have participated in a wide range of data sharing activities, including deposition of all eligible CMG data into the Analysis, Visualization, and Informatics Lab-space (AnVIL), sharing candidate genes through the Matchmaker Exchange and the CMG website, and sharing variants in Genotypes to Mendelian Phenotypes (Geno2MP) and VariantMatcher.

CONCLUSION

The work is far from complete; strengthening communication between research and clinical realms, continued development and sharing of knowledge and tools, and improving access to richly characterized data sets are all required to diagnose the remaining molecularly undiagnosed patients.