Dicentric isochromosome X with premature ovarian failure: report of two cases.

Two cases of dicentric isochromosome X, dic (Xp-), with premature ovarian failure are presented. The karyotype of case 1 is 46,X,dic(X)(qter-->p22::p22-->qter), and of case 2 is 45,X (77.5%)/46,X,dic(X)(qter-->p22::p22-->qter) (22.5%). An abnormal menstrual history including delayed menarche and secondary amenorrhea occurring at under 30 years of age was noted. Hormonal profiles revealed elevated levels of serum gonadotropins and decreased levels of estrogens. Gross appearance did not present an obvious picture of Turner's syndrome, except for short stature, poor development of secondary sexual characteristics and infertility. The possible mechanisms of dicentric isochromosome X are the breakage and reunion between either sister chromatid (isodicentric) or homologous chromosomes (homodicentric) which occur during meiosis of the germ cells in case 1 and mitosis after zygote formation in case 2.