Ahritis involving DIP, PIP, 1st carpometacarpal with sparing of MCP and wrist joints is typical of:
**Core Concept**
Osteoarthritis (OA) is a degenerative joint disease characterized by progressive wear and tear of articular cartilage, leading to joint pain, stiffness, and limited mobility. The disease typically affects weight-bearing joints and joints with high mechanical stress, such as the hands, knees, and hips.
**Why the Correct Answer is Right**
The correct answer is OA because it classically presents with involvement of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints, as well as the first carpometacarpal joint, with relative sparing of the metacarpophalangeal (MCP) joints and wrist joints. This pattern of joint involvement is due to the high mechanical stress on these joints, particularly the DIP and PIP joints, which bear the weight of the body and are subject to repetitive stress. In contrast, the MCP joints and wrist joints are less affected due to their lower mechanical stress.
**Why Each Wrong Option is Incorrect**
* **Option B:** Rheumatoid arthritis (RA) typically presents with symmetric involvement of the MCP and PIP joints, with relative sparing of the DIP joints and first carpometacarpal joint. RA also often involves the wrist joints and other joints of the hand and foot.
* **Option C:** Ankylosing spondylitis (AS) is a type of spondyloarthritis that primarily affects the spine and large joints, such as the hips and knees. AS does not typically involve the hands or fingers.
* **Option D:** Psoriatic arthritis (PsA) can present with a variety of joint patterns, including oligoarticular, polyarticular, and axial involvement. While PsA can involve the hands and fingers, it does not typically present with the classic pattern of DIP and PIP joint involvement seen in OA.
**Clinical Pearl / High-Yield Fact**
OA is often referred to as "wear and tear" arthritis, reflecting its degenerative nature. It is the most common type of arthritis, affecting millions of people worldwide, and is often associated with age, obesity, and joint trauma.
**✓ Correct Answer: A. Osteoarthritis**