A young man back from leisure trip has swollen knee joints & foreign body sensation in eyes. Likely cause is
**Core Concept**
The likely cause of this patient's presentation is an autoimmune response to a specific infectious agent, leading to inflammation and tissue damage in the affected areas.
**Why the Correct Answer is Right**
The patient's symptoms are suggestive of Parinaud's oculoglandular syndrome, a rare manifestation of cat-scratch disease (CSD) caused by Bartonella henselae. This syndrome is characterized by unilateral conjunctivitis, lymphadenopathy, and sometimes, swelling of the knee joint. The pathogenesis involves the immune response to the bacteria, leading to the production of cytokines and chemokines that cause inflammation and tissue damage.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as Chlamydia trachomatis is more commonly associated with conjunctivitis and urethritis, rather than Parinaud's oculoglandular syndrome.
* **Option B:** This option is incorrect as Staphylococcus aureus is a common cause of skin and soft tissue infections, but it is not typically associated with Parinaud's oculoglandular syndrome.
* **Option C:** This option is incorrect as Mycobacterium tuberculosis is a common cause of uveitis and conjunctivitis in endemic regions, but it is not typically associated with Parinaud's oculoglandular syndrome.
**Clinical Pearl / High-Yield Fact**
Parinaud's oculoglandular syndrome is a classic example of a "foreign body sensation" in the eye, which is often described as a feeling of a grain of sand or a foreign object in the eye. This symptom is a key clue to the diagnosis of CSD.
**Correct Answer:** D.