Random x-inactivation in a girl with duplication Xp11.21-p21.3: Report of a patient and review of the literature

We describe a 10-month-old girl with abnormal clinical findings and Xp dupl ication. She showed poor weight gain and developmental retardation, and had several minor anomalies including pigmentary dysplasia (hypomelanosis of I to), She had a partial short arm duplication in the paternally derived X ch romosome, 46,X,dup (X)(p11.21p21.3), with the normal and duplicated X chrom osomes randomly inactivated. These findings indicate that gross functional imbalance in the cells with an active dup(X) chromosome has caused global d evelopmental defects in the patient, and that functional chromosomal mosaic ism with respect to the duplicated Xp region has resulted in pigmentary dys plasia. Literature review of 52 patients with partial X duplications revealed (1) r andom or skewed but not completely selective X-inactivation in 9 of 45 pati ents examined for the X-inactivation pattern, independently of the size or location of duplicated segments, (2) apparently normal phenotype in 6 of 9 patients with random or skewed X-inactivation, and (3) an abnormal phenotyp e in 13 of 35 patients with completely selective inactivation of dup(X) chr omosomes. Am. J. Med, Genet. 86:44-50, 1999. (C) 1999 Wiley-Liss, Inc.