Arthrogryposis multiplex congenita in an infant with posterior agenesis of the corpus callosum.

A term male infant with arthrogryposis multiplex congenita and agenesis of the corpus callosum is described. Physical examination revealed multiplex dysmorphic features and fixed joints. A muscle biopsy showed type II fibers to be more than 12% smaller than type I fibers, consistent with the diagnosis of fiber type disproportion. The CT scan disclosed absence of the posterior corpus callosum and moderate atrophy of the cerebellar hemispheres. The pathogenetic mechanism for the muscle (and thus joint) abnormalities of this infant is discussed with respect to a central etiology.