A comparative study of mPCR, MLPA, and muscle biopsy results in a cohort of children with Duchenne muscular dystrophy: A first study

BACKGROUND: Multiplex ligation-dependant probe amplification (MLPA) is a highly sensitive and rapid alternative to multiplex polymerase chain reaction (PCR). Muscle biopsy should be reserved for mutation-negative cases. MATERIALS AND METHODS: An attempt was made to compare the sensitivity and pattern of mutations by mPCR and MLPA testing in a cohort with suspected Duchenne muscular dystrophy (DMD). Eighty-three children with DMD were enrolled for mPCR and MLPA testing. MLPA-negative cases underwent muscle immunohistochemistry (IHC) for dystrophin. RESULTS: Mean age of onset was 45.3 ± 25.2 months; and mean duration of illness was - 53.3 ± 30.8 months. About 11.9% patients had delayed mental milestones. Mean creatine kinase (CK) value was 12136.1 ± 8591.1 LU/L. mPCR detected deletions in 60/83 (72.3%). Proximal deletions were found in 8 (8.6%), distal deletions in 51 (54.8%), and, both proximal and distal deletions were found in 1. Majority of the deletions were <5 exons [34(36.6%)]; two showed large deletions of >10 exons (2.2%). Deletions in hot spot region occurred in 83.3%. MLPA in the same 83 samples detected deletions in an additional six cases and duplications in 6 (6.5%). Combined detection rate of deletion was 79.5%. Duplications were found in 7.2% of the whole sample. MLPA showed 14 (15.1%) proximal and 57 (61.3%) distal deletions, and proximal and distal deletion in 1. Large deletions (>10 exons) were seen in 6.5%, and single deletions were observed in 24 (36.4%). Most common multiple exon deletion was seen at 45-52 region in 7 samples (10.6%). Longest duplication extended from exon 60 to 66. In the 11 MLPA-negative cases, IHC confirmed dystrophinopathy in 36.36%, sarcoglycanopathy in 36.36%, and no deficiency in 27.27%. CONCLUSIONS: This is the first study from India and possibly in English literature, comparing the sensitivity and pattern of mutations by both mPCR and MLPA in the same cohort of DMD. It further validates that 36.4% of MLPA-negative cases were confirmed to have DMD by IHC. The clinical accuracy has been very high in our cohort. MLPA-negative samples should be subjected for next-generation sequencing before contemplating a biopsy.