Utility of Immunohistochemistry and Western Blot in Profiling Clinically Suspected Cases of Congenital Muscular Dystrophy

Objective: Immunocharacterization of congenital muscular dystrophy (CMD) to determine the frequency of various subtypes in a large Indian Cohort. Materials and Methods: This retrospective (2014-2017) study was carried on muscle biopsies of clinically suspected cases of CMD with histological evidence of dystrophy/myopathic features. Immunohistochemistry (IHC) to antibodies against laminin (alpha 2, alpha 5, beta 1, gamma 1), Collagen-VI (A1,2,3), and Western blot (WB) for alpha-dystroglycan and POMT1 was performed. Results: The study included 57 cases, of which 15 cases (26.3%) had mean age at presentation of 3.5 years, M: F = 1.5:1, elevated creatinine kinase (CK) (mean 1657 U/L), global developmental delay, multiple contractures, abnormal facies, white matter hyperintensities and showed laminin-alpha 2 deficiency (Merosin deficient CMD). In addition, secondary reduction in laminin-beta 1, over-expression of laminin-alpha 5, and preserved laminin-gamma 1 was noted. Ullrich CMD constituted 11/57 cases (19.2%) with mean age at presentation of 5.3 years, M: F = 1.2:1 and normal CK. They presented with proximal muscle weakness, soft velvety palms and soles, contractures, and joint hyperextensibility. Collagen-VI (A1,2,3) showed either complete (n = 3) or sarcolemmal specific (n = 8) loss of staining. Out of the remaining 31 cases, WB for a-dystroglycan was performed in 17 cases which showed deficiency in seven (12.3%). Three of these in addition revealed secondary partial loss of laminin-a2. WB for POMT1 showed deficiency in a single case clinically diagnosed Walker-Warburg syndrome, who presented with seizures and classical features of pachygyria, lissencephaly, and cerebellar cyst on MRI. Twenty-four cases (42.2%) remained uncharacterized and need genetic evaluation. Conclusion: The study helped in characterizing 57.8% of the proband. Immunotyping helps to direct mutational analysis for targeted genes and offers a potential route for prenatal diagnosis.