Hydrocephalus ex vacuo and clasp thumb deformity due to congenital cytomegalovirus infection.

A case of congenital hydrocephalus in a male infant with flexion deformity of the thumbs and great toes is reported. A maternal uncle had undefined intellectual impairment and X-linked hydrocephalus was considered among the differential diagnoses. However, this diagnosis was considered unlikely as the pyramids were preserved at autopsy. In addition, postmortem histopathology and viral culture established cytomegalovirus (CMV) infection as the underlying cause of the hydrocephalus. Although CMV infection is a well recognized cause of congenital hydrocephalus, the associated flexion deformities of the thumbs and great toes have not been previously described and may reflect injury to the corticospinal tracts.