Mutation in alpha 5 chain of collagen 4. The diagnosis –
## **Core Concept**
The question pertains to a genetic disorder related to a specific mutation in the alpha 5 chain of collagen 4. Collagen type IV is a crucial component of basement membranes in various tissues, including the kidneys, ears, and eyes. Mutations in the genes encoding for the alpha chains of collagen IV, particularly COL4A5, are associated with Alport syndrome.
## **Why the Correct Answer is Right**
Alport syndrome is a genetic disorder characterized by kidney disease, hearing loss, and eye abnormalities. It is caused by mutations in the COL4A5 gene (and sometimes COL4A3 or COL4A4 for autosomal forms), which encodes for the alpha 5 chain of type IV collagen. This mutation leads to the production of abnormal type IV collagen, affecting the structure and function of basement membranes, particularly in the kidneys, leading to progressive kidney disease. The X-linked form, most commonly associated with COL4A5 mutations, predominantly affects males.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond with the known association between collagen 4 alpha 5 chain mutations and Alport syndrome.
- **Option B:** Similarly, this option does not align with the established medical knowledge linking COL4A5 mutations to Alport syndrome.
- **Option C:** Not applicable as this is the correct answer.
## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that Alport syndrome often presents with hematuria, proteinuria, and progressive renal failure, alongside sensorineural hearing loss and eye abnormalities such as anterior lenticonus. Early diagnosis through genetic testing can help in managing the condition and preventing complications.
## **Correct Answer:** D. Alport syndrome.