Late onset muscular dystrophy with cerebral white matter changes due to partial merosin deficiency

Merosin-deficient congenital muscular dystrophy (CMD) is an autosomal recessive condition usually with onset at birth or within the first months of life. Affected children are severely disabled and usually do not achieve the ability to walk without support. They invariably have white matter abnormalities on brain magnetic resonance imaging (MRI). We report a 29-year-old man with a late childhood onset limb-girdle type muscular dystrophy and cerebral white matter changes on MRI. Immunocytochemical studies of the patient's muscle biopsy showed a reduction in expression of the laminin α₂ chain of merosin. The patient had three affected siblings, and microsatellite genotyping confirmed linkage to the laminin α₂ locus (LAMA2) on chromosome 6q2 in this family. This case probably represents a milder allelic variant of classical merosin-deficient CMD. Merosin status should be assessed in patients with late-onset limb girdle muscular dystrophy.