Detailed analysis of X chromosome inactivation in a 49,XXXXX pentasomy

Abstract

Background: Pentasomy X (49,XXXXX) has been associated with a severe clinical condition, presumably resulting from failure or disruption of X chromosome inactivation. Here we report that some human X chromosomes from a patient with 49,XXXXX pentasomy were functionally active following isolation in inter-specific (human-rodent) cell hybrids. A comparison with cytogenetic and molecular findings provided evidence that more than one active X chromosome was likely to be present in the cells of this patient, accounting for her abnormal phenotype.

A New Case of Prenatally Diagnosed Pentasomy X: Review of the Literature

“…The described features in 49, XXXXX karyotype include severe mental retardation with delayed speech development, short stature, facial dysmorphisms, osseous and articular abnormalities, congenital heart defects, and skeletal and limb abnormalities [ 1 ]. The craniofacial anomalies may include microcephaly, micrognathia, plagiocephaly, hypertelorism, upslanting palpebral fissures, a flat nasal bridge, and ear malformations.…”

Subtelomeric Microduplications in Three Sisters with Moderate Mental Retardation

“…A recent study reports a case of a mentally retarded woman with an elongated face, clinodactyly, and a congenital heart defect, who showed supernumerary X chromosomes, suggesting that the observed phenotype might be associated with excess activity in X regions or increased asynchronism of X chromosome replication (Moraes et al 2009). …”

Report of a New Case With Pentasomy X and Novel Clinical Findings

“…These patients usually have normal genitalia, but secondary sex characteristics can be incomplete. Pentasomy X syndrome has been associated with severe clinical conditions, presumably resulting from failure or disruption of X chromosome inactivation [ 7 ]. No adults with pentasomy X have been reported since the prognosis is universally poor.…”