Subtle overlapping deletions in the terminal region of chromosome 6q24.2-q26: Three cases studied using FISH

Interstitial deletions in the terminal region of chromosome 6 are rare. We describe three new cases with subtle interstitial deletions in the q24-q26 region of the long arm of chromosome 6. The karyotypes were analyzed at a 5 50 band level. Patient1 is a 9-month-old boy with an interstitial deletion, del(6)(q24.2q25.1), developmental delay, low birth weight, hypotonia, hear t murmur, respiratory distress, craniofacial and genital anomalies. This is the first report of a case with deletion del(6)(q24.2q25.1). Patient 2 is a 17-year-old young man with an interstitial deletion del(6)(q25.1q25.3), d evelopmental delay, short stature, mental retardation, autism, head, face, chest, hand and feet anomalies and a history of seizures. For the first tim e autism was described as a manifestation in 6q deletions. Patient 3 is bab y boy with a de novo interstitial deletion, del(6)(q25.1q26), anomalies of the brain, genital organs, limbs and feet. This is the first report of a ca se with deletion, del(6)(q25.1q26). In all three patients, fluorescence in situ hybridization (FISH) using chromosome 6 painting probe ruled out an in sertion. The ESR (6q25.1) and TBP (6q27) probes were used to confirm the br eakpoints. Since TBP signal is present in all cases, it confirmed an inters titial deletion proximal to this probe. Patient 1 has a deletion of the ESR locus; Patient 2 and 3 have signals for the ESR locus on both chromosomes 6. Therefore the deletion in Patients 2 and 3 are between ESR and TBP loci distal to that of Patient 1. FISH validated the deletion breakpoints assess ed by conventional cytogenetics. Am. J. Med. Genet. 87:17-22, 1999. (C) 199 9 Wiley-Liss, Inc.