Molecular Diagnosis of Limb-Girdle Muscular Dystrophy Using Next-Generation Sequencing Panels

Introduction

Limb-girdle muscular dystrophies (LGMDs) are clinically and genetically heterogeneous muscle disorders. We aimed to share the diagnostic yield of an NGS gene panel containing LGMD-related genes and our experience with LGMD.

Methods

Between February 2019 and October 2022, patients with a suspicion of LGMD and their relatives were reviewed in terms of demographic, clinical, and individual genetic data, age of symptom onset, sex, clinical features, LGMD types, cardiac involvement, muscle biopsy results, family history, and consanguinity. Our NGS gene panel consisted of ANO5, CAPN3, CAV3, DAG1, DES, DNAJB6, DYSF, FKTN, FLNC, FRKP, GAA, GMPPB, HNRNPDL, ISPD, LIMS2, LMNA, MYOT, PLEC, POMGNT1, POMK, POMT1, POMT2, SGCA, SGCB, SGCD, SGCG, TCAP, TNPO3, TRAPPC11, TRIM32, and TTN genes.

Results

The diagnosis rate was 61.1% (11/18). Twelve (80%) patients with LGMD were male and three (20%) were female. The median age was 15.9 (range, 1.5-39) years. Our patient collective was drawn up out of patients with the following variants: LGMDR1 (n = 6; 40%), LGMDR2 (n = 4; 26.6%), LGMDR3 (n = 4; 26.6%), and LGMDR12 (n = 1; 6.7%).

Conclusion

The present study showed that the NGS panel has a high success rate in the diagnosis of LGMD and contributes to early diagnosis.

Hemoglobin A1C can differentiate subjects with GCK mutations among patients suspected to have MODY

OBJECTIVES

The aim of this study is to determine the clinical and molecular characteristics enabling differential diagnosis in a group of Turkish children clinically diagnosed with MODY and identify the cut-off value of HbA_1c, which can distinguish patients with GCK variants from young-onset type 1 and type 2 diabetes.

METHODS

The study included 49 patients from 48 unrelated families who were admitted between 2018 and 2020 with a clinical diagnosis of MODY. Clinical and laboratory characteristics of the patients at the time of the diagnosis were obtained from hospital records. Variant analysis of ten MODY genes was performed using targeted next-generation sequencing (NGS) panel and the variants were classified according to American Collage of Medical Genetics and Genomics (ACMG) Standards and Guidelines recommendations.

RESULTS

A total of 14 (28%) pathogenic/likely pathogenic variants were detected among 49 patients. 11 variants in GCK and 3 variants in HNF1A genes were found. We identified four novel variants in GCK gene. Using ROC analysis, we found that best cut-off value of HbA_1c at the time of diagnosis for predicting the subjects with a GCK variant among patients suspected to have MODY was 6.95% (sensitivity 90%, specificity 86%, AUC 0.89 [95% CI: 0.783-1]). Most of the cases without GCK variant (33/38 [86%]) had an HbA_1c value above this cutoff value. We found that among participants suspected of having MODY, family history, HbA_1c at the time of diagnosis, and not using insulin therapy were the most differentiating variables of patients with GCK variants.

CONCLUSIONS

Family history, HbA_1c at the time of diagnosis, and not receiving insulin therapy were found to be the most distinguishing variables of patients with GCK variants among subjects suspected to have MODY.

Late onset Bartter syndrome: Bartter syndrome type 2 presenting with isolated nephrocalcinosis and high parathyroid hormone levels mimicking primary hyperparathyroidism

OBJECTIVES

Nephrocalcinosis is associated with conditions that cause hypercalcemia and the increased urinary excretion of calcium, phosphate, and/or oxalate. A monogenic etiology is found in almost 30% of childhood-onset nephrocalcinosis which is also a common manifestation of primary hyperparathyroidism. We discuss a child with nephrocalcinosis and features mimicking primary hyperparathyroidism.

CASE PRESENTATION

A 7-year-old girl presented with nephrocalcinosis. Hypercalciuria, hyperphosphaturia, mild hypercalcemia, hypophosphatemia and elevated parathyroid hormone levels along with normal serum creatinine and absence of hypokalemic alkalosis suggested primary hyperparathyroidism. However, she was ultimately diagnosed with Bartter syndrome type 2 based on the presence of homozygous pathogenic variation in KCNJ1gene.

CONCLUSIONS

This is the second reported case of late-onset Bartter syndrome type 2 without hypokalemic alkalosis. Patients with Bartter syndrome may present with high parathyroid hormone levels and hypercalcemia in addition to hypercalciuria. Thus, the present case suggests that the KCNJ1 gene should be included in genetic analysis even in older children with isolated nephrocalcinosis.

Autoimmune/autoinflammatory syndrome induced by adjuvants after multi-component meningococcal serogroup b vaccination in a 7-year-old girl: a case report

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