Klinefelter Syndrome Mosaicism 46,XX/47,XXY: A New Case and Literature Review

XXXYY variant of Klinefelter syndrome: A case report

This case report is about a 19-month-old boy, product of an in vitro fertilization twin pregnancy and born to young non-consanguineous parents, who presented with speech and motor developmental delay. On genetic evaluation, he was found to have the exceedingly rare variant 49, XXXYY of Klinefelter syndrome. Given the rarity of this condition and the limited literature available, this case report will surely add value to the literature.

An Adolescent Boy with Klinefelter Syndrome and 47,XXY/46,XX Mosaicism: Case Report and Review of Literature

Klinefelter syndrome is the most commonly reported sex chromosome abnormality. It is heavily underdiagnosed due to the substantial variability of clinical presentations but is generally characterized by small, firm testes, hypergonadotropic hypogonadism, and the absence of spermatogenesis. Most patients with Klinefelter syndrome have a 47,XXY genotype. If they present with mosaicism, two different cell lines are usually identified, an aneuploid 47,XXY cell line and a normal male 46,XY cell line. There are very few cases of 47,XXY mosaicism with the additional female cell line 46,XX described in the literature. We report a case of an adolescent with the male phenotype and a rare variant mosaic 47,XXY/46,XX karyotype who presented with painless bilateral gynaecomastia. 47,XXY and 46,XX mosaic cell lines were identified with GTG-banding and further characterized using fluorescent in situ hybridization. We summarized the available clinical presentations of reported male patients with 47,XXY/46,XX mosaicism. To improve the clinical management and quality of life in individuals with rare and cryptic genomic imbalances, the genetic diagnosis would need to be extended to atypical cases.