Neuropediatrics 2015; 46 - FV03-06
DOI: 10.1055/s-0035-1550666

Diagnostic Panels: A Powerful Tool to Identify the Underlying Genetic Cause in Neuromuscular Diseases

J. Mohr 1, N. Glöckle 1, C. Heller 1, T. Grau 1, E. Gleixner 1, K. Bengesser 1, C. Wilhelm 1, F. Battke 1, S. Biskup 1, K. Hörtnagel 1
  • 1CeGaT GmbH, Tübingen, Germany

Aims: The identification of the genetic causes of neuromuscular disorders (NMD) and thus the confirmation of the clinical diagnosis is critical for the patient. A distinct genetic diagnosis allows prognosticating the course of disease, calculation of the familial recurrence risk, and may offer targeted therapy. However, the genetic diagnostics of NMD is complicated by the heterogeneity of the diseases and the multitude of relevant genes and their large size (e.g., TTN, NEB, RYR1, and DMD). To ensure comprehensive genetic diagnostics nevertheless, we developed a diagnostic panel which allows the analysis of all genes relevant for NMD simultaneously.

Methods: A total of 268 relevant genes associated with NMD were subdivided according to their clinical phenotypes. MLPA was performed where appropriate, followed by customized target enrichment and next-generation sequencing.

Results: In this study, we analyzed over 600 patients with NMD. In 29% of the cases, the underlying cause was successfully identified whereas in 22% of the cases probably pathogenic but unclear variants were detected. Overall, 49% of the cases remained unsolved. We could observe clearly pathogenic mutations in 71 different genes, with TTN (7.4%), CAPN3 (5.7%), DMD (5.7%), and RYR1 (5.1%) being the most frequently mutated genes.

One of the analyzed patients is an 8-year-old boy suffering from progressive muscle weakness. FSHD, DMD/BMD, and SMA as genetic cause had been excluded beforehand. We were able to solve the case by detecting the two compound heterozygous mutations c.21019C > T; p.Q7007X and c.98827 + 5G > A in TTN. By applying cDNA analysis, we could show that the mutation c.98827 + 5G > A leads to skipping of the upstream exon.

Conclusion: As expected, the patient cohort exhibited high-genetic heterogeneity. The diagnostic panels offer an efficient method to come up to this heterogeneity. In particular, the method provides the opportunity to analyze very large genes, such as TTN. With help of NGS-based diagnostic panels, patients with a so far genetically unsolved disease now have the possibility to receive a genetic diagnosis.

Keywords: NGS, panel diagnostics, mutation, genetics.