Intrachromosomal triplication for the distal part of chromosome 15q.
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.
Schluth
C
C
Laboratoire de Génétique, Hôpital Emile Muller, Mulhouse, France.
Mattei
M G
MG
Mignon-Ravix
C
C
Salman
S
S
Alembik
Y
Y
Willig
J
J
Ginglinger
E
E
Jeandidier
E
E
D000015:Abnormalities, Multiple / Q000235:genetics* / Q000473:pathology; D000328:Adult; D002648:Child; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics*; D005145:Face / Q000002:abnormalities; D005500:Follow-Up Studies; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007231:Infant, Newborn; D008607:Intellectual Disability / Q000473:pathology; D007621:Karyotyping; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D012600:Scoliosis / Q000473:pathology; D009396:Wilms Tumor / Q000473:pathology