Familial microtia with meatal atresia in two sibships.

Hereditary malformations of the external ear, such as microtia and auditory meatal atresia, unassociated with other congenital defects or syndromes, are rarely reported in the medical literature. McKenzie (1958) described such deformities of the external ear as one of the phenotypic variations within the category of a 'first arch syndrome' caused by a dominant gene with variable pentrance. Complete penetrance of the first arch syndrome gene is proposed to result in the clinical entities known as Treacher Collins syndrome, Pierre Robin syndrome, or mandibular dystosis (McKenzie, 1966). A recent paper (Peterson and Schimke, 1968) challenged this concept and concluded that there were several genetically distinct and simply inherited branchial arch syndromes which had phenotypic overlap. Fraser (1964) introduced the probability that only a proportion of cases with a first arch syndrome defect were genetic and that many unilateral cases were phenocopies. The physician who must provide genetic counselling to parents of an infant with malformations of the external ear not associated with other defects and with a negative family history could be understandably optimistic after a review of available literature. The purpose of this paper is to report two sibships, in each of which malformations of the external ear occurred in two successive pregnancies.