Genetic marker for reiters syndrome
**Core Concept**
Reiter's syndrome, also known as reactive arthritis, is a type of arthritis that occurs as a reaction to an infection elsewhere in the body, often in the gastrointestinal tract or the urethra. It is characterized by the presence of certain autoantibodies and a specific genetic marker. The genetic marker associated with Reiter's syndrome is linked to the HLA-B27 gene.
**Why the Correct Answer is Right**
The HLA-B27 gene is a major histocompatibility complex (MHC) class I gene that plays a crucial role in the immune system. It is involved in the presentation of antigens to T-cells, which helps to activate the immune response. In individuals with the HLA-B27 gene, the immune system is more likely to produce autoantibodies against certain proteins, leading to the inflammation and joint pain characteristic of Reiter's syndrome. The presence of HLA-B27 is a strong predictor of the development of Reiter's syndrome, especially in individuals who have been infected with certain bacteria, such as Chlamydia or Salmonella.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a genetic marker for Reiter's syndrome.
* **Option B:** This option is incorrect because it is not a recognized genetic marker for Reiter's syndrome.
* **Option C:** This option is incorrect because it is a different genetic marker associated with a different condition.
**Clinical Pearl / High-Yield Fact**
The HLA-B27 gene is also associated with other autoimmune conditions, such as ankylosing spondylitis and psoriatic arthritis. This is why individuals with a family history of these conditions may be more likely to develop Reiter's syndrome.
**Correct Answer: C. HLA-B27 gene**