Familial congenital laryngeal abductor paralysis: different expression in a family with one male and three females affected.

A brother and two sisters of remotely consanguineous parents had congenital laryngeal abductor paralysis and moderate mental retardation. In the two older sibs, mental deficiency could have resulted from birth asphyxia, but the youngest girl was already microcephalic at birth and had no apparent asphyxia. The mother, who was healthy and of normal intelligence, was found on laryngoscopy to have unilateral laryngeal abductor paralysis. This is the first family with both mentally retarded and nonretarded affected members with congenital laryngeal abductor paralysis. Inheritance is most likely autosomal dominant with variable expression, but autosomal recessive inheritance, with both parents carriers and the mother an affected homozygote, and X linked inheritance are also possible.