True microcephaly has been shown to be an autosomal recessive trait.1 Despite mental retardation, general health and neurologic function of the affected children are usually not impaired, except for smaller size than unaffected sibs and generalized hypertonus. The affected persons are not demented.
The present report concerns eight cases of microcephaly observed in two sibships of an inbred group. In addition to the usual features of microcephaly, ocular abnormalities were observed in all and probably result from the same genetic defect.
All four parents share a common ancestral couple born in late 1700's (Fig 1). Through this relationship the parents of both sibships are third cousins. Both families are members of a "horse-and-buggy" Mennonite sect living in Lancaster and Berks Counties, Pennsylvania, and totalling about 4,000 persons.2 All are descendants of immigrants to the United States from the upper Rhineland in the first half of the
McKUSICK VA, STAUFFER M, KNOX DL, CLARK DB. Chorioretinopathy With Hereditary Microcephaly. Arch Ophthalmol. 1966;75(5):597-600. doi:10.1001/archopht.1966.00970050599003