**Question:** CASPAR criteria is used in diagnosis of -

A. Behçet's disease
B. Sjögren's syndrome
C. Systemic lupus erythematosus (SLE)
D. Rheumatoid arthritis (RA)

**Core Concept:** CASPAR criteria are a set of diagnostic criteria developed for specific medical conditions to assist clinicians in determining the likelihood of a particular disease in a patient. In this case, the criteria are designed for the diagnosis of connective tissue diseases (CTDs).

**Why the Correct Answer is Right:**

C. Systemic lupus erythematosus (SLE) is the correct answer because the CASPAR criteria specifically focus on the diagnosis of connective tissue diseases (CTDs). SLE is a common CTD characterized by inflammation and damage to tissues and organs. The CASPAR criteria were developed to improve the accuracy of diagnosing SLE and distinguish it from other CTDs.

**Why Each Wrong Option is Incorrect:**

A. Behçet's disease is a different condition, also known as Behçet's syndrome, characterized by recurrent oral ulcers, genital ulcers, and uveitis. It does not involve the criteria provided in CASPAR for diagnosing SLE.
B. Sjögren's syndrome is another CTD characterized by dryness of the eyes and mouth. It does not meet the criteria of CASPAR for diagnosing SLE, as the criteria are specific to SLE.
D. Rheumatoid arthritis (RA) is an autoimmune inflammatory disorder affecting the joints. It is not associated with the CASPAR criteria developed for diagnosing SLE.

**Clinical Pearl / High-Yield Fact:**

CASPAR criteria are a valuable tool for diagnosing SLE, as they combine clinical, serological, and immunopathological features. These criteria help distinguish SLE from other autoimmune diseases and guide appropriate treatments. Understanding the specific criteria for SLE diagnosis is essential for accurately diagnosing and managing patients with connective tissue diseases.