A 5.3Mb deletion in chromosome 18q12.3 as the smallest region of overlap in two patients with expressive speech delay.

ABSTRACT

Interstitial 18q deletions encompassing band 18q12.3 define the del(18)(q12.2q21.1) syndrome. Usual manifestations are mild dysmorphic features, mental retardation, behaviour abnormalities and lack of serious malformation. Seizures have also been found. Recently, more specifically, impairment of expressive language has been reported. We report on two patients with de novo 18q interstitial deletions characterized by oligonucleotide array CGH. The smallest, a 5.3Mb deletion (35.7-40.9Mb) within band q12.3, was found in a 4-year-old girl who suffered mainly from expressive dysphasia. A larger 9.5Mb deletion (34.6-43.9Mb) was observed in a 20-year-old man with a more severe clinical picture including seizures and limited speech. Among the four genes located in the 5.3Mb region, RIT2 (Ras-like without CAAX 2) and SYT4 (synaptotagmin IV), both strongly expressed in the brain, are pointed out as likely candidate genes for language development.