Molecular and Histopathological Characterization of Patients Presenting with the Duchenne Muscular Dystrophy Phenotype in a Tertiary Care Center in Southern India.

Objective: To study the histopathological characteristics and mutation spectrum of patients presenting with the Duchenne muscular dystrophy (DMD) phenotype.

Methods: This was a descriptive study conducted over a period of 8 years. Multiplex ligation-dependent probe amplification (MLPA) was done in patients presenting with the DMD phenotype. If MLPA was negative, patients were offered muscle biopsy for histopathological studies and/or next generation sequencing (NGS) based multigene panel testing for muscular dystrophies.

Results: Of the 510 patients included, mutation in the DMD gene was detected by MLPA in 372 (72.9%), of whom 342 (67.1%) had exonic deletions and 30 (5.9%) had exonic duplications. Exons 45-55 were most commonly involved in large deletions and exons 1-10 were the commonest exons involved in duplications. In the MLPA-negative cohort, 27 proceeded for muscle biopsy. NGS was done in 14 patients, 10 of whom had pathogenic mutations in the DMD gene, 3 were non dystrophinopathies and no pathogenic variant could be identified in one patient.

Conclusions: For patients presenting with the DMD phenotype, MLPA of the DMD gene has a high diagnostic rate of about 73%, and non-dystrophinopathies may constitute a small but significant proportion.