A prospective study on the immunophenotypic characterization of limb girdle muscular dystrophies 2 in India.

OBJECTIVE: In this prospective study conducted over 2 years, 300 nonconsecutive cases of autosomal recessive limb girdle muscular dystrophies (AR-LGMD) were characterized, based on phenotypic features, biochemical findings, electrophysiological studies, muscle immunohistochemistry (IHC), and western blot (WB) analysis.

METHODS: Muscle biopsy was performed in 280 index cases. 226 biopsies were subjected for IHC, and, 176 of these for WB analysis.

RESULTS: A total of 246 patients were finally analyzed. This figure included 20 affected siblings. LGMD2B was the most common form and comprised of 33.3% (n = 82) of the entire cohort. This was followed by alpha-dystroglycanopathies with 61 (24.79%) patients (LGMD2I in 15, 2K in 10 and combined deficiency of both in the remaining). LGMD 2C-F was present in 35 (14.23%) cases and LGMD2A in 22 (10.2%) cases, and were identified by routine WB, densitometry method and autocatalytic assay. LGMD2G was present in 8 patients (3.25%), and LGMD2H and 2J in 2 cases each, respectively.

CONCLUSIONS: For the first time, we have identified patients with LGMD2G, 2H, 2I, and 2K by the WB technique. These may be the common forms of autosomal recessive (AR)-LGMD's among Indian patients and need identification for prognostication and appropriate counseling. Although not a nationwide study, our data is sufficient to provide information about the relative proportions of various LGMD2 subtypes in India. Diagnosing LGMD2 based on classical clinical features, IHC and WB is fairly sensitive and specific; however, further genetic studies are required to confirm the diagnosis.