Duplication of 7p21.2-->pter due to maternal 7p;21q translocation: implications for critical segment assignment in the 7p duplication syndrome.
We describe a 1-year-old boy with mental and physical retardation, a large anterior fontanel, brachycephaly with flat occiput, short and stubby fingers, generalized hypotonia, ocular hypertelorism, low-nasal bridge, long philtrum, high-narrow palate, apparently low-set ears, and a small mandible. Cytogenetic analysis utilizing high resolution chromosome banding technique showed an unbalanced karyotype consisting of 46,XY,add(21)(q22.3) that originated from maternal balanced translocation between chromosomes 7 and 21. Fluorescence in situ hybridization (FISH) using micro-dissected library probe pool from chromosome 7 confirmed the additional material on 21q was derived from chromosome 7. Our results indicated that the patient had an unbalanced translocation, 46,XY, der(21)t(7;21)(p21.2;q22.3)mat, which resulted in duplication for distal 7p. Our patient is similar to reported cases with a 7p15-->pter or larger duplication of 7p, suggesting that the critical segment causing the characteristic phenotype of 7p duplication syndrome, including large anterior fontanel, exists at 7p21.2 or 7p21.2-->pter.
Cai
T
T
National Laboratory of Medical Genetics, Hunan Medical University, P. R. China. tao.cai@nih.gov
Yu
P
P
Tagle
D A
DA
Xia
J
J
D000015:Abnormalities, Multiple / Q000235:genetics*; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics*; D019465:Craniofacial Abnormalities / Q000235:genetics*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D010641:Phenotype; D013577:Syndrome; D014178:Translocation, Genetic