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

Abstract

Pentasomy X is an extremely rare sex chromosome abnormality, a condition that only affects females, in which three more X chromosomes are added to the normally present two chromosomes in females. We investigated the novel clinical findings in a 1-year-old female baby with pentasomy X, and determined the parental origins of the X chromosomes. Our case had thenar atrophy, postnatal growth deficiency, developmental delay, mongoloid slant, microcephaly, ear anomalies, micrognathia and congenital heart disease. A conventional cytogenetic technique was applied for the diagnosis of the polysomy X, and quantitative fluorescent polymerase chain reaction (QF-PCR) using 11 inherited short tandem repeat (STR) alleles specific to the chromosome X for the determination of parental origin of X chromosomes. A cytogenetic evaluation revealed that the karyotype of the infant was 49,XXXXX. Comparison of the infant’s features with previously reported cases indicated a clinically recognizable specific pattern of malformations referred to as the pentasomy X syndrome. However, to the best of our know-ledge, this is the first report of thenar atrophy in a patient with 49,XXXXX. The molecular analysis suggested that four X chromosomes of the infant originated from the mother as a result of the non disjunction events in meiosis I and meiosis II. We here state that the clinical manifestations seen in our case were consistent with those described previously in patients with pentasomy X. The degree of early hypotonia constitutes an important early prognostic feature in this syndrome. The pathogenesis of pentasomy X is not clear at present, but it is thought to be caused by successive maternal non disjunctions.

Report of a New Case of Pentasomy X Revealed by Status Epilepticus

“…A moderate deficit in psychomotor development is the most described neurological manifestation. A suspected case of spinal muscular atrophy has been reported in Turkey in an infant with pentasomy X, but confirmatory genetic testing could not be performed [5]. Epilepsy and cerebral leukodystrophy, discovered in our patient, have not been described in the majority of the 49, XXXXX forms published in the literature.…”

“…The X chromosomes of this pentasomy are secondary either to a meiotic nondisjunction, where the two X chromosomes do not separate during the first or second division of gametogenesis, or to a mitotic nondisjunction in the zygote during its development. If the X chromosomes do not separate properly and go on to the next cell division and do not divide fully yet, when the sperm fertilizes the egg, the fetus is left with four X chromosomes from one parent and a fifth X from the other parent (49, XXXXX) [5]. Since in the majority of cases the parents do not carry chromosomal abnormalities, the risk of having another daughter with an X pentasomy is not higher than in the general population.…”

Non-Invasive Prenatal Screening: The First Report of Pentasomy X Detected by Plasma Cell-Free DNA and Karyotype Analysis

“…Pentasomy X was first described in 1963, by Kesaree and Wooley [ 17 ], and only around 30 children with a 49,XXXXX karyotype were reported so far [ 18 ]. The pathogenesis of pentasomy X is probably caused by successive meiotic non disjunctions, either maternal or combined maternal and paternal in origin [ 19 ].…”

Manifestaciones bucales en un paciente pediátrico con pentasomía x. Reporte de un caso

“…To our knowledge from 25 to 30 cases have so far been reported, then an approximate incidence of 1 in 85.000 was reported comparing to 49,XXXXY syndrome in male live births. Other numerical abnormalities of the sex chromosomes such as 47,XXX, 47,XXY, 47,XYY and 45,X are relatively common, and occur in approximately 1 of 400 live births ( 2,4,5 ). Pentasomy X significantly impacts systems and organs, facilitating developmental delays.…”

“…Most polysomies are due to a double nondisjunction in morphogenesis; even though the pathogenesis of pentasomy X is unclear, it is probably caused by successive maternal non-disjunctions. The addition of more than one extra sex chromosome occurs exceptionally and information is generally limited to isolated case reports 2 , 3 .…”