A 28 years old man has anterior lenticonus and ESRD now. His maternal uncle also died of similar illness. Diagnosis is:
**Core Concept**
Anterior lenticonus is a rare, congenital condition characterized by an abnormal curvature of the anterior surface of the lens in the eye, often associated with Alport syndrome, a genetic disorder affecting the type IV collagen in the kidney, ear, and eyes.
**Why the Correct Answer is Right**
The patient's symptoms, including anterior lenticonus and end-stage renal disease (ESRD), along with a family history of a similar illness, suggest Alport syndrome. Alport syndrome is caused by mutations in the COL4A3, COL4A4, or COL4A5 genes, which encode for the alpha chains of type IV collagen. This collagen is crucial for the structure and function of the glomerular basement membrane in the kidneys, the basement membrane of the inner ear, and the lens capsule in the eyes. The presence of anterior lenticonus and ESRD in the patient and his maternal uncle indicates an X-linked pattern of inheritance, as the COL4A5 gene is located on the X chromosome.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Alport syndrome is not primarily associated with a different type of collagen.
**Option B:** This option is incorrect as the patient's symptoms do not suggest a condition primarily affecting the ears.
**Option C:** This option is incorrect as the patient's family history and symptoms do not indicate a condition primarily affecting the skin.
**Clinical Pearl / High-Yield Fact**
Alport syndrome is a classic example of a genetic disorder that affects multiple systems, including the kidneys, ears, and eyes. It is essential to suspect Alport syndrome in patients with anterior lenticonus, ESRD, and a family history of a similar illness.
**Correct Answer: C. Alport syndrome**