Clinical and pathological heterogeneity in late-onset partial merosin deficiency

Mutations in the LAMA2 gene result in a complete loss of merosin and underlie a severe congenital type of muscular dystrophy (MDC1A).We investigated the clinical, genetic, and histological basis of late-onset muscular dystrophy in one family. The proband and her affected brother exhibited late-onset predominantly proximal muscle weakness. In addition, the proband experienced seizures. Magnetic resonance imaging of her brain demonstrated white-matter abnormalities. Sequencing of LAMA2 identified two new heterozygous point mutations in the two affected members. Muscle histology demonstrated dystrophic features, rimmed vacuoles, and partial loss of laminin α immunoreactivity. Partial merosin deficiency can present with a mild, late-onset limb-girdle-type pattern of weakness, with or without epilepsy, and pathologically may exhibit features observed in inclusion-body myopathy.