Turner syndrome caused by a pseudo-isodicentric Xp chromosome containing two copies of the SHOX gene

Abstract

The article describes a clinical case of Turner syndrome (TS) in a 15-year-old patient with mosaicism involving a pseudoisodicentric Xp chromosome. The disorder was characterized by delayed puberty, primary amenorrhea, gonadal dysgenesis, uterine hypoplasia, hypergonadotropic hypogonadism, and stigmas of dysembryogenesis. Comprehensive cytogenetic, molecular-cytogenetic, and molecular-genetic studies were conducted. Mosaicism with two cell lines was found in lymphocytes and buccal epithelial cells: one with X chromosome monosomy, the other with one normal X and one pseudoisodicentric Xp chromosome carrying two copies of the SHOX gene. Chromosomal microarray analysis detected monosomy of most of the Xq, and trisomy of the Xp and proximal region of the Xq, with a breakpoint at the Xq13.3 locus (75,444,376–155,233,731). The patient’s normal growth is attributed to the presence of two copies of the SHOX gene on the derivative chromosome. This clinical case enhances the understanding of the genetic mechanisms underlying the phenotypic manifestations of patients with pseudoisodicentric Xp chromosomes.