**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 urogenital tract. This condition is characterized by the triad of arthritis, urethritis, and conjunctivitis, along with other systemic symptoms.

**Why the Correct Answer is Right**
Reiter's syndrome is a form of seronegative spondyloarthritis, which means that it does not produce the typical rheumatoid factor seen in rheumatoid arthritis. The condition is associated with the presence of HLA-B27 antigen, which is a genetic marker that predisposes individuals to develop certain types of arthritis. The symptoms of Reiter's syndrome can include asymmetric oligoarthritis, urethritis, conjunctivitis, and mucocutaneous lesions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Reiter's syndrome is indeed characterized by a triad of symptoms, which includes arthritis, urethritis, and conjunctivitis.
**Option B:** This option is incorrect because Reiter's syndrome is often associated with the presence of HLA-B27 antigen, which is a genetic marker that predisposes individuals to develop certain types of arthritis.
**Option C:** This option is incorrect because Reiter's syndrome can indeed involve the presence of mucocutaneous lesions, such as keratoderma blennorrhagicum.

**Clinical Pearl / High-Yield Fact**
Reiter's syndrome is often triggered by an infection with Chlamydia trachomatis or other bacteria, and it can be associated with other systemic symptoms such as fever, fatigue, and weight loss.

**Correct Answer: A.**