Intrachromosomal triplication for the distal part of chromosome 15q

• Published in: American journal of medical genetics. Part A Vol. 136A; no. 2; pp. 179 - 184
• Main Authors: Schluth, C., Mattei, M. G., Mignon‐Ravix, C., Salman, S., Alembik, Y., Willig, J., Ginglinger, E., Jeandidier, E.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15-07-2005
• Subjects: Abnormalities, Multiple - genetics; Abnormalities, Multiple - pathology; Adult; body asymmetry; Child; Chromosome Aberrations; Chromosome Banding; Chromosomes, Human, Pair 15 - genetics; Face - abnormalities; Follow-Up Studies; Humans; In Situ Hybridization, Fluorescence; Infant, Newborn; Intellectual Disability - pathology; interstitial telomere; intrachromosomal triplication; Karyotyping; Male; Mosaicism; nephroblastoma; Phenotype; Scoliosis - pathology; tetrasomy 15q24.3‐qter; Wilms Tumor - pathology
• ISSN: 1552-4825; 1552-4833
• DOI: 10.1002/ajmg.a.30745

We report the case of a boy whose karyotype at birth showed additional material on one chromosome 15. He underwent treatment for unilateral nephroblastoma at 6 years old. At 23 years old, he presented with body asymmetry, facial dysmorphism, arachnodactyly, severe scoliosis, and mental retardation. Molecular cytogenetic analyses of peripheral lymphocytes demonstrated a complex mosaic with three clones. A major cell lineage (68%) showed a chromosome 15 with additional material fused to its telomere long arm that was constituted by an inverted duplicated 15q24.3‐qter segment. Therefore, the resulting add(15)(q) harbored an intrachromosomal triplication with the middle segment being inverted in orientation. A minor cell lineage (7%) showed an abnormal chromosome 3 resulting from a telomeric fusion between its short arm and an inverted duplicated 15q24.3‐qter segment. The third cell lineage (25%) showed a normal 46,XY constitution. Finally, this resulted in tetrasomy for the distal 15q24.3‐qter region in 75% of the patient's lymphocytes. To our knowledge, distal 15q tetrasomy is rare and only eight cases have been reported in the literature, all due to a supernumerary analphoid marker consisting of an inverted duplication. We report here the first observation of distal 15q tetrasomy associated with a 46 chromosomes constitution. We compare the phenotype of our patient to previous cases of distal tetrasomy 15q and discuss the mechanisms underlying this chromosomal rearrangement. © 2005 Wiley‐Liss, Inc.