Master Klinefelter's Syndrome with Picmonic for Medicine

Klinefelter's syndrome is a genetic disorder, in which patients are born with at least one extra X chromosome, giving them a total of 47 chromosomes rather than the 46. 47, XXY is the most common sex chromosome aneuploidy in males born with this syndrome.

Individuals with Klinefelter's typically have a eunuchoid body habitus, with long extremities and wide hips. These patients are typically taller than average males of the same age. Patients with this condition display underdeveloped sexual organs, and specifically, because of testicular atrophy, male hormone production is deficient.

Gynecomastia, or increased breast tissue, is present in about a third of affected individuals. Additionally, men with Klinefelter’s display female hair distribution, showing decreased facial and body hair growth.

Patients born with Klinefelter’s syndrome will develop microorchidism, or testicular atrophy. This testicular atrophy, where there is diminished size and function of the testicles, leads to a primary hypogonadism, characterized by low serum testosterone.

Those with Klinefelter’s syndrome develop seminiferous tubule dysgenesis. This is a dysfunction by which the seminiferous tubules exhibit an abnormal cytoarchitecture and extensive hyalinization; the testes are small, with few spermatozoa formed.

In Klinefelter’s syndrome cognitive and developmental delays are seen. Patients often have trouble with language learning and reading at a young age, and also display motor delays. This includes achieving developmental milestones much later than normal (sitting, crawling, walking). Later in life this can translate as inability to participate in sports, and trouble with academic success.

In Klinefelter’s syndrome there is diminished size and function of the testicles, leading to a primary hypogonadism. Hypogonadism described as diminished functional activity of the gonads, characterized by low serum testosterone in this syndrome. Additionally, in patients there is impaired gamete production and/or regulation.

Inhibin B is produced by the gonads and downregulates FSH synthesis and inhibits FSH secretion. Due to hypogonadism in these patients, lab workup will reveal decreased inhibin B.

In Klinefelter's Syndrome, primary hypogonadism leads to low serum testosterone and decreased inhibin. A consequence of this decreased inhibin is that FSH synthesis is not downregulated, resulting in increased FSH levels.

Leydig cells are found adjacent to the seminiferous tubules in the testes, and produce testosterone in the presence of LH. In Klinefelter's Syndrome, Leydig cells are dysfunctional, and this results in decreased testosterone, increased LH and increased estrogen.

In Klinefelter's Syndrome, primary hypogonadism leads to low serum testosterone, and consequently high serum FSH, LH, and estrogen.

In Klinefelter's Syndrome, primary hypogonadism leads to low serum testosterone, and consequently high serum FSH, LH, and estrogen.

In Klinefelter's Syndrome, primary hypogonadism leads to low serum testosterone, and consequently high serum FSH, LH. The increase in serum FSH up-regulates aromatase, which leads to increased conversion of testosterone to estrogen.

A Barr body is the inactive X chromosome in a female somatic cell, rendered inactive in a process called lyonization. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated during embryogenesis. Consequently in Klinefelter's Syndrome, or XXY, there is a single Barr body, with one normally functioning X chromosome.