In a cohort of 961 clinically suspected Duchenne muscular dystrophy patients, 105 were diagnosed to have other muscular dystrophies (OMDs), with LGMD2E (variant SGCB c.544A>C) being the most common.

Abstract

Background: Targeted next generation sequence analyses in a cohort of 961 previously described patients with clinically suspected Duchene muscular dystrophy (DMD) revealed that 145/961 (15%) had variants in genes associated with other muscular dystrophies (OMDs).

Methods: NGS was carried out in DMD negative patients after deletion/duplication analysis followed by WES for No variant cases.

Results: The majority of patients with OMDs had autosomal recessive diseases that included Limb-Girdle Muscular Dystrophies (LGMDs), Bethlem, Ullrich congenital Myopathies and Emery-Driefuss muscular dystrophy. 3.5% of patients were identified with other disorders like Charcot-Marie Tooth and Nemaline myopathy. A small percentage of patients, 0.6% remain undiagnosed. Of a total of 78 genetic variants identified, 44 were found to be novel. Interestingly, a third of patients with OMDs were found to have LGMD2E/R4, a severe form of LGMD that afflicts young children with clinical symptoms similar to DMD. Almost one third of the unrelated LGMD2E/R4 patients had the same point mutation (c.544A>C) in the SGCB gene, suggestive of a founder effect, described here for the first time in India.

Conclusion: This study underscores the need for a complete genetic work up to precisely diagnose patients and to initiate appropriate counseling programs, disease management and prevention strategies.