Background: The objective of this study is to describe the utility of multiplex ligation-dependent probe amplification technique(MLPA) in the genetic diagnosis of SMA and correlate it clinically in a large cohort from India.

Methodology: It was a retrospective study conducted from a single quaternary care center for neurological disorders.  Medical records of the patients who attended the neuromuscular clinic(October 2012 to December 2017) and genetically confirmed to have SMA based on MLPA were included. MLPA was used to detect deletions in exon 7 and exon 8 of the SMN1 gene using SALSA MLPA P034 and P035 probe sets(MRC Holland, Netherlands) as per manufacturer’s instructions.

Results: During the study period a total of 150 patients were genetically confirmed to have SMA. It comprised of 92 boys and 58 girls. Forty-one patients (27.3%) belonged to type 1, forty-four (29.3%) to type 2, twenty-three (15.3%) to type 3a, thirty-nine (26%) to type 3b and three patients (3.1%) belonged to type 4 SMA. Tongue fasciculation was prominent in type 1, type 2 and type 3a SMA; whereas calf hypertrophy was marked in type 3b and type 4 SMA patients. MLPA analysis revealed combined deletions of exon 7 and 8 in 119 patients(79.3%), isolated exon 7 deletions in 30 patients(20%) and one isolated exon 8 deletion in type 2 SMA. The detailed results are described in table 1.

Conclusions:

The authors describe a large cohort of genetically confirmed SMA patients based on MLPA from India and emphasize its utility.