Silent microcephaly: a distinct autosomal dominant trait.

Thirteen patients from three unrelated families were found to have microcephaly, without any neurological or dysmorphic manifestations. Autosomal dominant inheritance is concluded since the trait was transmitted directly in all three families, including one male-to-male instance. The recognition of this uncomplicated form of microcephaly as a Mendelian trait further extends its etiological heterogeneity.