Interstitial deletion 1p36.32 in two brothers with a distinct phenotype--overgrowth, macrocephaly and nearly normal intellectual function.

We report on two adult patients, who both presented with overgrowth and one of them additionally with macrocephaly while carrying an 1p36 microdeletion of about 2.1 Mb. They are full brothers born to unaffected parents. Although both brothers attended special schools, they lived independently without a legal guardian and were able to succeed in regular jobs. One of the brothers received a professional education. Genetic analysis of the parents revealed neither the microdeletion nor a cryptical translocation or inversion. We suggest that the recurrent deletion is a result of germline mosaicism, a phenomenon reported only once in the context of the 1p36 microdeletion syndrome. Our report confirms the recurrence of the apparently de novo 1p36 microdeletion due to a likely germline mosaicism of one of the parents. Furthermore, it illustrates the possibility of the distinct phenotype with a nearly normal intellectual outcome of the 1p36 microdeletion syndrome that might be due to the region involved in our patients.