Disorders Involving Sex Chromosomes
Klinefelter syndrome is caused by meiotic nondisjunction and is a common cause of male hypogonadism. Turner syndrome is a common cause of female hypogonadism.
DISORDERS INVOLVING SEX CHROMOSOMES
Klinefelter syndrome is caused by meiotic nondisjunction and is a common cause of male hypogonadism. The most common karyotype is 47,XXY. Lab studies show elevated FSH and LH with low levels of testosterone. Clinical findings include testicular atrophy, infertility due to azoospermia, eunuchoid body habitus, high-pitched voice; female distribution of hair; and gynecomastia.
Turner syndrome is a common cause of female hypogonadism. The most common karyotype is 45,X. The second X chromosome is necessary for oogenesis and the normal development of the ovary. Clinically, patients fail to develop secondary sex characteristics and have short stature with widely spaced nipples. Other features include gonadal dysgenesis with atrophic streak ovaries; primary amenorrhea; and infertility.
Clinical features involving other organ systems include cystic hygroma and webbing of the neck; hypothyroidism; congenital heart disease (preductal coarctation of the aorta and bicuspid aortic valve); and hydrops fetalis. Females with 45, X/46, XY mosaicism are at risk for gonadoblastoma.