Phenotypic findings due to trisomy 7p15.3-pter including the TWIST locus

We report on a three-month-old boy with a 46,XY,der(Y)t(Y,7)(p11.32;p15.3) karyotype and growth deficiency, postnatal microcephaly with large fontanel s, wide sagittal and metopic sutures, hypertelorism, choanal stenosis, micr ognathia, bilateral cryptorchidism, hypospadias, abnormal fingers and toes, and severe developmental delay. FISH studies showed partial trisomy 7p res ulting from a de novo unbalanced translocation. The application of molecula r probes from the TWIST gene region (7p15.3-p21.1) and probes from the pseu doautosomal region (PAR) demonstrated that the 7p15.3-pter fragment was tra nslocated onto Yp with the breakpoint within similar to 20 kb from the Yp t elomere. We discuss the possible role of the TWIST gene in abnormal skull d evelopment and suggest that trisomy 7p cases with delayed closure of fontan els can be a result of TWIST gene dosage effect. (C) 2001 Wiley-Liss, Inc.