Most common cardiac defect in Turner syndrome
**Core Concept**
Turner syndrome is a genetic disorder that affects females, characterized by the absence of one X chromosome. Individuals with Turner syndrome are at an increased risk of various cardiac abnormalities due to the involvement of the X chromosome in the development of the cardiovascular system.
**Why the Correct Answer is Right**
The most common cardiac defect in Turner syndrome is a bicuspid aortic valve (BAV). This condition occurs due to the abnormal development of the aortic valve during embryogenesis. The BAV is thought to result from the disruption of the normal development of the left coronary cusp and the right coronary cusp, leading to the formation of a single, abnormal valve. The exact mechanism is not fully understood, but it is believed to be related to the abnormal expression of genes involved in the development of the cardiovascular system.
**Why Each Wrong Option is Incorrect**
**Option A:** Coarctation of the aorta is a cardiac defect that involves the narrowing of the aortic isthmus, but it is not the most common cardiac defect in Turner syndrome.
**Option B:** Hypoplastic left heart syndrome is a severe cardiac defect that involves the underdevelopment of the left side of the heart, but it is not typically associated with Turner syndrome.
**Option C:** Mitral valve prolapse is a condition that involves the bulging of the mitral valve into the left atrium during systole, but it is not the most common cardiac defect in Turner syndrome.
**Clinical Pearl / High-Yield Fact**
BAV is a common cardiac defect in Turner syndrome and is often associated with other cardiovascular abnormalities, including aortic dilation and aortic dissection.
**Correct Answer: A. Bicuspid aortic valve**