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47 XYY chromosome disorder
1%
3/221
47 XXY chromosome disorder
77%
170/221
Chloride ion transporter defect
2%
4/221
Androgen insensitivity
16%
36/221
Defective migration of GnRH cells
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This man is presenting with features consistent with Klinefelter's syndrome (47 XXY), including long extremities, gynecomastia, and infertility with elevated FSH and LH. Klinefelter's syndrome is a sex chromosome disorder characterized by the presence of an extra X chromosome. Patients typically present with hypergonadotropic hypogonadism, a eunuchoid body type (including long extremities), female body hair distribution, gynecomastia, azoospermia, and testicular atrophy. Laboratory evaluation will typically show elevated aromatase levels, as well as evelated FSH, LH, and estrogen levels, but with low testosterone levels. Wattendorf and Muenke discuss the presentation of Klinefelter's syndrome. Klinefelter's occurs in about 1 in 1,000 boys. In about 10% of cases, this karyotype is detected at or before time of birth. In about 25% of cases, detection occurs in adulthood. The majority of affected men will be infertile. Overall, Klinefelter's explains about 3% of cases of male infertility, usually in men with oligospermia or azoospermia. Høst et al. discuss hypogonadism in Klinefelter's. While the classical description is a tall, narrow shouldered, broad hipped man with sparse body hair, small testes, and gynecomastia, there can be alternate phenotypes that may present with only some of the classic features. However, in nearly all cases, small testes and elevated gonadotropins are present. The disorder remains highly underdiagnosed because of the variability in presentation. Figure A shows the classic body habitus associated with Klinefelter's, including gynecomastia, narrow shoulders, broad hips, and long arms. Illustration A shows a karyotype of a Klinefelter's patient. Note the presence of an additional X chromosome. Incorrect Answers: Answer 1: XYY presents with very tall stature, severe acne, sometimes with antisocial behavior, and normal fertility. Answer 3: Chloride ion transporter defect is associated with cystic fibrosis, which causes male infertility, but does not otherwise fit this clinical picture. Answer 4: Androgen insensitivity presents as phenotypically female. Answer 5: Defective migration of GnRH cells occurs in Kallmann syndrome, which causes hypogonadotropic hypogonadism.
4.3
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