Combined deletion 18q22.2 and duplication/triplication 18q22.1 causes microcephaly, mental retardation and leukencephalopathy

Chromosome 18 abnormalities rank among the most common autosomal anomalies with 18q being the most frequently affected. A deletion of 18q has been attributed to microcephaly, mental retardation, short stature, facial dysmorphism, myelination disorders, limb and genitourinary malformations and congenital aural atresia. On the other hand, duplications of 18q have been associated with the phenotype of Edwards syndrome. Critical chromosomal regions for both phenotypes are contentious. In this report, we describe the first case of an 11-year old male with a combined interstitial duplication 18q22.1, triplication 18q22.1q22.2 and terminal deletion 18q22.2q23 with phenotypic features of isolated 18q deletion syndrome and absence of phenotypic features characteristic of Edwards syndrome despite duplication of the suggested critical region. This report allows for reevaluation of proposed critical intervals for the phenotypes in deletion 18q syndrome and Edwards syndrome.