Diastematomyelia in two sisters.

Diastematomyelia is a rare spinal cord anomaly that usually occurs in a non-syndromal, sporadic manner; however, few familial cases have been reported. We report on diastematomyelia in 2 sisters with variable expressivity. The spinal column is divided by osseous or fibrous tissue. This may be responsible for the variable expressivity. Most cases previously reported were females. This suggests X-linked dominant inheritance with lethality in hemizygous males or female sex limitation of a multifactorial trait.