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. Muscle Nerve, 2011