No abstract

We describe three unrelated patients with apparently identical interstitial deletions of the segment (18) (q12.2q21.1). They were a short and markedly mentally retarded 5 year old girl, a macrocephalic and obese 2½/ year old boy with moderate mental retardation, and a macrocephalic, severely mentally retarded 5 year old boy. Findings common to all five liveborn patients so far identified as carrying this deletion include a pattern of minor dysmorphic features (prominent forehead, ptosis of the upper eyelids, full periorbital tissue, epicanthic folds, strabismus), muscular hypotonia, seizures, behavioural disorders, and lack of major malformations.Terminal deletion of the long arm of chromosome 18, del(18)(q21qter) is frequently found, and is associated with a characteristic phenotype. ' Interstitial deletions in the long arm of chromosome 18, by contrast, are rare. Only three patients with deletions of chromosome 18 (q12.2q21.1), including one mosaic in a prenatally detected fetus, have been reported so far.2' We present three further patients with deletion of this segment.