Proximal myotonic myopathy with MRI white matter abnormalities of the brain.

Proximal myotonic myopathy (PROMM) is an autosomal dominantly inherited multisystemic disorder characterized by myotonia, proximal muscle weakness, and cataracts. This disorder is not linked to the gene locus of myotonic dystrophy (DM). We describe three new families with PROMM. In all patients, CTG repeats of the DM gene in DNA from blood leukocytes were normal. MRI of the brain revealed a consistent pattern of marked white matter hyperintensity on T2-weighted images in four patients; two additional patients had similar but mild to moderate MRI abnormalities. The morphology of these abnormalities is unknown. Clinical symptoms of brain disease were not consistent and included mental changes with hypersomnia, parkinsonian features, stroke-like episodes, and seizures. The causative relationship of these clinical features with the MRI white matter abnormalities remains to be established. Our observations suggest that PROMM may involve the brain.