Karyotype 47,XXX

**Definition:** Trisomy X is a sex chromosome anomaly with a variable phenotype caused by the presence of an extra X chromosome in females (47,XXX instead of 46,XX). Most individuals are only mildly affected or asymptomatic, the most common physical features including tall stature, epicanthal folds, hypotonia and clinodactyly, with seizures, renal and genitourinary abnormalities, and premature ovarian failure being also associated findings.