**Core Concept**
Sulphasalazine is an anti-inflammatory agent primarily used in inflammatory bowel disease and rheumatoid arthritis. It acts as a weak sulfonamide and has anti-inflammatory effects mediated through inhibition of prostaglandin synthesis and modulation of immune responses. Its use is limited to conditions with well-established inflammatory pathology, particularly in the gastrointestinal and joint systems.

**Why the Correct Answer is Right**
Sulphasalazine is effective in treating ulcerative colitis and rheumatoid arthritis due to its anti-inflammatory and immunomodulatory properties. It is also used in Crohn's disease, though less commonly than in ulcerative colitis. However, sarcoidosis is a systemic granulomatous disease of unknown etiology, not primarily driven by inflammation in the same way as the other conditions. Sulphasalazine has no proven role in sarcoidosis and is not recommended for its treatment.

**Why Each Wrong Option is Incorrect**
Option A: Crohn's disease – Sulphasalazine is used in mild to moderate cases, particularly in early disease or as an adjunct.
Option B: Rheumatoid arthritis – It is a first-line disease-modifying antirheumatic drug (DMARD) for RA.
Option D: Ulcerative colitis – It is a standard therapy for mild to moderate cases of ulcerative colitis.

**Clinical Pearl / High-Yield Fact**
Never use sulphasalazine in sarcoidosis. It is ineffective and may mask underlying disease progression. Always remember: sulphasalazine is for GI and joint inflammation, not granulomatous diseases like sarcoidosis.

✓ Correct Answer: C. Sarcoidosis