Familial myopathy with changes resembling inclusion body myositis and periventricular leucoencephalopathy. A new syndrome.

Five of 6 male siblings were affected by a progressive myopathy beginning in early childhood. Muscle biopsies in all patients showed the characteristic changes of inclusion body myositis. Computerized tomography and magnetic resonance imaging revealed a markedly abnormal appearance of cerebral white matter in the 4 affected patients tested, but clinical and other laboratory examinations failed to demonstrate evidence of central white matter dysfunction. Muscle biopsies and brain imaging were normal in all clinically unaffected family members. On the basis of the genetics, muscle biopsy findings and cerebral white matter changes, we conclude that this constellation represents a hitherto undescribed syndrome.