Microcephaly syndromes.

The objective of this article is to review microcephaly from a genetics point of view, especially with regard to the process of identification of syndromes in which small head circumference occurs. Microcephaly can be due to either genetic or environmental causes. It can be the only positive finding or may be part of a syndrome of congenital anomalies. The genetic etiology can be caused by autosomal dominant, autosomal recessive, or X-linked genes or various types of chromosome anomalies. Some of the gene mutations have been identified recently. Syndromic microcephaly is associated with a large number of conditions. Some can be diagnosed, or at least suspected, based on their characteristic facial dysmorphism, and others can be searched for using databases of genetic disorders.