What is the genetic disorder in which an individual has an overall masculine development gynaecomastia, and is sterile ?

Answer & Solution:

The correct answer is (b) Klinefelter's syndrome

Klinefelter's syndrome is the most common chromosomal disorder of males associated with hypogonadism and infertility. It is due to extra-X-chromosome. Classically, it is 47, XXY. Other variants can have 48 XXXY, rarely 49 XXXY or mosaics can be there with some cells containing normal 46, XY and others 47, XXY. Classically, it results from meiotic non- disjunction of sex chromosomes [40% during spermatogenesis and 60% during oogenesis]. Mostly, non-disjunction occur during 1st meiotic division. Extra X- chromosomes increase the female like features, i.e. feminization [as shown by atrophic testes, lack of secondary sexual characteristics, gynecomastia]. Further, Extra inactive X-chromosome appear as Barr body.  Presence of single Y- chromosome is enough for male phenotype. Thus XY, XXY, XXXY all are males. Clinical features include male Hypogonadism, Loss of secondary sexual characteristics, Subnormal IQ, Disproportionately long arms and legs, Gynecomastia, increased risk of breast carcinoma, germ cell tumors (like embryonal cell carcinoma, teratoma and mediastinal germ cell tumors) and autoimmune diseases like SLE. Patients can develop cardiovascular problems. Most commonly associated is mitral valve prolapse followed by varicose veins. Due to less testosterone (hypogonadism), feedback inhibition is less and pituitary produces more LH and FSH.