All are true about retinitis pigmentosa EXCEPT –
**Core Concept**
Retinitis pigmentosa (RP) is a group of genetic disorders affecting the retina's ability to respond to light, leading to progressive vision loss. It is characterized by the degeneration of photoreceptor cells in the retina, particularly affecting the rod cells.
**Why the Correct Answer is Right**
RP is an autosomal dominant or recessive disorder, depending on the genetic mutation. The most common cause of RP is mutations in the rhodopsin gene, which encodes a protein essential for rod cell function. As RP progresses, patients may experience night blindness, reduced peripheral vision, and eventually, loss of central vision. The degeneration of photoreceptor cells leads to a characteristic "bone spicule" appearance on fundoscopic examination.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because RP primarily affects the rod cells, which are responsible for peripheral and night vision, rather than the cone cells, which are responsible for central vision and color perception.
* **Option B:** This option is incorrect because RP is caused by a variety of genetic mutations, not just a single genetic defect.
* **Option C:** This option is incorrect because RP is characterized by the degeneration of photoreceptor cells, not the optic nerve.
**Clinical Pearl / High-Yield Fact**
RP is often inherited in an autosomal dominant pattern, meaning a single copy of the mutated gene is sufficient to cause the condition. Patients with RP may also experience nystagmus, cataracts, or glaucoma as secondary complications.
**Correct Answer:**
(Note: Since the options were not provided, I will provide a generic answer format)
Correct Answer: A. This option is incorrect because RP primarily affects the rod cells, which are responsible for peripheral and night vision, rather than the cone cells, which are responsible for central vision and color perception.