CYTOGENETIC AND MOLECULAR CYTOGENETIC STUDIES OF A CASE OF INTERSTITIAL DELETION OF PROXIMAL 15Q

A 4-month-old child with multiple anomalies was determined to have an interstitial deletion of chromosome 15, i.e., del(15) (q12q14). The de letion appears not to be a typical deletion of 15q12 such as seen in A ngelman and Prader-Willi syndromes, but appears to be more distal, inv olving either loss of all of 15q12 and part of 15q14, or part of 15q12 and most of 15q14. In either case, 15q13 is missing. Fluorescent in s itu hybridization with probes for 15 centromere (D15Z), pericentromeri c satellite sequences (D15Z1), and chromosome 15 painting probes shows the deleted chromosome to involve only 15 and no other acrocentric ch romosome. Hybridization with probes for the AS and PWS loci (D15S11 an d GABAB3, Oncor) show both sites to be intact in the deleted 15. The c ase is compared with two other reports with overlapping interstitial d eletions of proximal 15q, neither of which shows typical features of A ngelman or Prader-Willi syndromes.