Familial inclusion body myositis among Kurdish-Iranian Jews.

We report two cases of adult-onset, slowly progressive limb-girdle muscle weakness with a remarkable sparing of quadriceps muscles that developed in patients from different families of Iranian-Kurdish-Jewish origin. Each patient had a similarly affected sibling. The findings by means of muscle biopsies showed abnormalities typical of inclusion body myositis, including abundant lined vacuoles and characteristic cytoplasmic inclusions of 15- to 18-nm filaments. Remarkably, many vacuolated muscle fibers showed immunoreactivity to neural cell adhesion molecule, a fetal muscle antigen. The common origin of these patients from an isolated ethnic group with frequent consanguinity and the familial incidence is indicative of a genetic causation or predisposition, probably with an autosomal recessive inheritance. This familial myopathy is one of several clinical syndromes that share the typical pathological findings of inclusion body myositis. The pathogenic relationship between these different familial forms and the more common sporadic form of inclusion body myositis is not known.