Karthik Tallapaka1, Prajnya Ranganath2, Angalena Ramachandran3, Megha S Uppin4, Sreeja Perala1, Shagun Aggarwal1, Dhanya Lakshmi1, A K Meena5, Ashwin B Dalal3. 1. Department of Medical Genetics, Nizam's Institute of Medical Sciences and Diagnostics division, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, India. 2. Department of Medical Genetics, Nizam's Institute of Medical Sciences and Diagnostics division, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, India. Correspondence to: Dr Prajnya Ranganath, Associate Professor and Head, Department of Medical Genetics, Nizam's Institute of Medical Sciences, Panjagutta, Hyderabad, Telangana 500 082, India. prajnyaranganath@gmail.com. 3. Diagnostics division, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, India. 4. Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India. 5. Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
Abstract
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.
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.