Ring Chromosome X

Cases with ring chromosome X (RCX) were detected using karyotyping, fluorescence in situ hybridization (FISH), Southern blotting, PCR analysis, and chromosome microarray analysis (CMA) to define their ring structure, dynamic mosaicism, and genomic imbalance. Prenatal and postnatal diagnosis should include direct FISH testing for mosaicism, as well as standard culture, as the RCX can be lost during culture. The genetic counseling for pregnancies with RCX can be difficult since it cannot be determined if the phenotype will be the mild or have a more severe presentation. The majority of postnatal cases are females who present with varying levels of Turner syndrome phenotypes. RCX have rarely been reported in males. Patients with a RCX can broadly be categorized in two main phenotypic groups; the majority with a Turner-like phenotype with variable expression of short stature, normal intelligence, webbed neck, widely spaced nipples, narrow palate, renal and cardiac defects, peripheral edema, low posterior hairline and ovarian dysgenesis. Others present with more severe intellectual disability, syndactyly, and hypotonia. Application of hormone therapy for growth and development, as well as, cardiac and renal abnormalities should be considered for all patients with RCX.