Microcephaly

Abstract This chapter reviews the incidence, risk factors, genetics, recurrence risk, and epidemiology of isolated and syndromic microcephaly. The differential diagnosis of microcephaly includes multiple teratogenic agents such as alcohol, hyperthermia, maternal PKU, and new and old congenital infections as well as specific chromosome aneuploidies such as 4p- and 5p- where microcephaly is almost universally seen. Metabolic disorders include congenital disorders of glycosylation and pyruvate dehydrogenase deficiency. Multiple autosomal recessive primary microcephaly syndromes (MCPH) are being delineated. Important syndromes with microcephaly include Cornelia de Lange and Smith Lemli Opitz syndromes but many other complex genetic syndromes include microcephaly. A clinical case presentation features an infant with autosomal recessive primary microcephaly with an unknown genetic cause.