This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
A patient presents with foreign body sensation in eye and swollen knee joint after a leisure trip. Which of the following is the most probable diagnosis? 
Select and explain. 
A. SLE, B. Sarcoidosis, C. Reiter's disease, D. Behcet's disease
C: Reiter's disease
Answer: C: Reiter's disease 
Explanation: As the patient in the question has developed ahritis following a recent travel, it could be a reactive ahritis secondary to organisms endemic in the zone of travel. Along with this, patient is showing features of conjunctivitis indicating a diagnosis of Reiter's syndrome. Reactive ahritis (Reiter's syndrome) consists of conjunctivitis, urethritis (or cervicitis in female patients), ahritis, and characteristic mucocutaneous lesions. Ref: Harrison's Internal Medicine, 18th Edition, Chapter 176