Klinefelter Syndrome (47,XXY)
| Category | Details & Clinical Pathophysiology |
|---|---|
| Genetics | Male phenotype with an extra X chromosome (47,XXY). Usually results from meiotic non-disjunction. Advanced maternal age is a risk factor. |
| Clinical Features | Tall stature, gynecomastia, small firm testes, azospermia (infertility), and female-typical secondary sexual characteristics (e.g., sparse facial hair). |
| Hormonal Profile | Primary testicular failure leads to decreased testosterone, which results in elevated FSH and LH (hypergonadotropic hypogonadism) and increased estrogen due to aromatase activity. |
High-Yield Core Realities:
- Infertility & Pathology: The small, firm testes are due to seminiferous tubule atrophy and hyalinization of the stroma. This is the most common genetic cause of male hypogonadism and infertility.
- Associated Risks: Patients have a higher risk of developing breast cancer (due to the presence of extra X-linked gene expression and gynecomastia) and are at increased risk for developmental delays and learning disabilities.
- Management: Testosterone replacement therapy is essential to promote the development of secondary sexual characteristics and to mitigate risks such as osteoporosis.
- Educational Resource: For further study, high-yield practice questions, and clinical pearls on sex chromosome aneuploidies, visit mymedschool.org.