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What is What is the genotype of Klinefelter's syndrome? and explain in detail?
Klinefelter syndrome is the most common chromosomal disorder associated with male hypogonadism and infertility.
It is defined classically by a 47, XXY karyotype with variants demonstrating additional X and Y chromosomes. (Other variants can have 48 XXXY, rarely 49 XXXXY or mosaics can be there with some cells containing normal 46, XY and others 47, XXY). Classically, it results from meiotic nondisjunction of sex chromosomes (40% during spermatogenesis and 60% during oogenesis). Mostly, non-disjunction occur during 1 st meiotic division
The patient has male phenotype with feminizing features due to extra X-chromosome (note: the presence of one Y chromosome is sufficient for the male phenotype. Thus XY, XXY, XXXY all are males). Extra inactive chromosome appears as a Barr body.
Important clinical features include macroorchidism with normal external genitalia, mental retardation, gynecomastia, lack of secondary sexual characteristics with eunuchoid (PGI 01) body habits, disproportionately long arms and legs, hypogonadism, increased incidence of tumors (breast carcinoma, germ cell tumors), increased incidence of autoimmune disorders (e.g. SLE), and cardiac problems (most common is mitral valve prolapse). Testosterone levels are decreased, whereas levels of gonadotropins (FSH/LH) are elevated.