Mosaicism for a small supernumerary ring X chromosome in a dysmorphic, growth‐retarded male: mos47,XXY/48,XXY, + r(X)

• Published in: Clinical genetics Vol. 52; no. 6; pp. 432 - 435
• Main Authors: Manea, Susan R., Gershin, Irina F., Babu, Arvind, Willner, Judith P., Desnick, Robert J., Cotter, Philip D.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-1997; Blackwell
• Subjects: Abnormalities, Multiple - genetics; Biological and medical sciences; Child, Preschool; Chromosome aberrations; Developmental Disabilities - genetics; Dosage Compensation, Genetic; Face - abnormalities; fluorescence in situ hybridization; Growth Disorders - genetics; Humans; In Situ Hybridization, Fluorescence; Male; Medical genetics; Medical sciences; Mosaicism; ring chromosome; Ring Chromosomes; X Chromosome; X inactivation; Chromosomal aberration; Human; Case study; Phenotype; Ring chromosome; Aneuploidy; Abnormal chromosome; Mosaicism; Male; Developmental disorder; Supernumerary X chromosome; Child
• ISSN: 0009-9163; 1399-0004
• DOI: 10.1111/j.1399-0004.1997.tb02564.x

Supernumerary ring X [r(X)] chromosomes are often found in patients with Turner syndrome. The phenotypic effects of the r(X) chromosome are variable, and largely depend on the presence or absence of the X inactivation (XIST) locus. Ring(X) chromosomes in males are rare and have been previously reported in only four cases, with 47,XY, + r(X) or mos47,XY, + r(X)/46,XY karyotypes. These patients all had developmental delay and dysmorphic features. We describe a 2.5‐year‐old male patient with facial dysmorphia, growth retardation, microcephaly, global developmental delay, and microphallus. Cytogenetic analysis from peripheral blood lymphocytes and fibroblasts identified mosaicism for two cell lines: mos48,XXY, + r(?X)/47,XXY. Fluorescence in situ hybridization (FISH) with an X chromosome paint showed the ring chromosome to be X chromosome derived. This is the first case of an r(X) chromosome described in a 47,XXY patient. FISH analysis of the r(X) chromosome with an XIST probe showed that the XIST locus was absent. Functional disomy of genes in the r(X) chromosome most likely accounts for the abnormal phenotype in the proband.