[Phelan McDermid Syndrome: five patients description and report on the first case described in conjoined twins].

Phelan McDermid Syndrome is caused by the loss of genetic material in a chromosome from pair 22, at the band q13.3. We describe five patients with deletion 22q13.3 in order to establish a genotype-phenotype association, and report the first case described in conjoined twins. We analyzed the perinatal history, psychomotor behavior, language, and the presence of minor dysmorphism. Karyotypes and in situ hibridization (FISH) for critical region 22q13.3 were performed to all patients. There were hypotonia, developmental delay, and delay or absence of language. A 22q13.3 deletion was detected in all patients described, two cases had a deletion and the other three had a ring of chromosome 22, one in a pure cell line, while the twins presented mosaicism. Karyotype and FISH for 22q11.2 critical region should be performed, with 22q13.3 control probe to detect the deletion of Phelan McDermid syndrome in all patients with clinical phenotype suggestive and evocative of velo-cardio-facial syndrome.