Which of the following is an example of disorders of sex chromosomes
Klinefelter syndrome is an impoant genetic cause of reduced spermatogenesis and male infeility. In some patients the testicular tubules are totally atrophied and replaced by pink, hyaline, collagenous ghosts. In others, apparently normal tubules are interspersed with atrophic tubules. In some patients all tubules are primitive and appear embryonic, consisting of cords of cells that never developed a lumen or progressed to mature spermatogenesis. Leydig cells appear prominent, as a result of the atrophy and crowding of the tubules and elevation of gonadotropin concentrations. Patients with Klinefelter syndrome have a higher risk for breast cancer (20 times more common than in normal males), extragonadal germ cell tumors, and autoimmune diseases such as systemic lupus erythematosus. The classic pattern of Klinefelter syndrome is associated with a 47,XXY karyotype (90% of cases). This complement of chromosomes results from nondisjunction during the meiotic divisions in the germ cells of one of the parents. Maternal and paternal nondisjunction at the first meiotic division are roughly equally involved. There is no phenotypic difference between those who receive the extra X chromosome from their father and those who receive it from their mother. Maternal age is increased in the cases associated with errors in oogenesis. In addition to this classic karyotype, approximately 15% of patients with Klinefelter syndrome have been found to have a variety of mosaic patterns, most of them being 46,XY/47,XXY.Other patterns are 47,XXY/48,XXXY and variations on this theme. As is the case with normal females, all but one X chromosome undergoes inactivation in patients with Klinefelter syndrome. Why then, do the patients with this disorder have hypogonadism and associated features? The explanation for this lies in genes on the X chromosome that escape lyonization and in the pattern of X inactivation. Ref Robbins 9/e pg 165
Marfan's syndrome
Testicular feminization syndrome
Klinefelter's syndrome
Down's syndrome
Genetics