Pigmentary mosaicism in hypomelanosis of Ito. Further evidence for functional disomy of Xp.
We report on a female with mental and motor retardation, facial dysmorphism, abnormal pigmentation reminiscent to hypomelanosis of Ito (HI), and karyotypic mosaicism involving a small supernumerary marker chromosome. The marker chromosome was defined by fluorescence in situ hybridisation (FISH) as a ring X chromosome with breakpoints in the juxtacentromeric region. FISH analysis showed that the ring does not include the XIST locus at the X-inactivation centre and, therefore, may not be subject to X inactivation. X-inactivation studies with the HUMARA (human androgen receptor) and FMR1 assay showed a skewed X-inactivation pattern (85:15) with preferential inactivation of the paternal X chromosome. These results are discussed with respect to the role of functional disomy of Xp in the pathogenesis of HI.
Fritz
B
B
Department of Clinical Genetics, Medical Center of Human Genetics, Philipps University Marburg, Germany. fritzb@mailer.uni-marburg.de
Küster
W
W
Orstavik
K H
KH
Naumova
A
A
Spranger
J
J
Rehder
H
H
D002675:Child, Preschool; D004303:Dosage Compensation, Genetic; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009030:Mosaicism; D010859:Pigmentation Disorders / Q000235:genetics*; D012303:Ring Chromosomes; D014960:X Chromosome