A 35 – year old male develops involvements of PIP, DIP and metacarpophalangeal joints with sparing of wrist and carpometacarpal joints. The probable diagnosis is:
**Question:** A 35-year-old male develops involvements of PIP, DIP, and metacarpophalangeal joints with sparing of wrist and carpometacarpal joints. The probable diagnosis is:
A. Rheumatoid arthritis
B. Psoriatic arthritis
C. Gout
D. Ankylosing spondylitis
**Correct Answer:**
**Core Concept:** Inflammatory arthritis is a group of conditions characterized by chronic inflammation of the synovial joints, including PIP, DIP, and metacarpophalangeal joints. This question focuses on distinguishing between different types of inflammatory arthritis based on their specific joint involvement patterns.
**Why the Correct Answer is Right:**
The correct answer, **D. Ankylosing spondylitis**, is characterized by inflammation primarily affecting the axial skeleton (spine, sacroiliac joints, and the pubic symphysis). Inflammatory arthritis involving the peripheral joints (PIP, DIP, and metacarpophalangeal joints) is seen in other diseases.
**Why Each Wrong Option is Incorrect:**
A. Rheumatoid arthritis (RA) typically affects multiple joints symmetrically, including wrists and carpometacarpal joints. The sparing of these particular joints in the given case makes RA less likely.
B. Psoriatic arthritis (PsA) generally involves the peripheral joints, but sparing of the metacarpophalangeal joints is more common in PsA compared to ankylosing spondylitis. However, the sparing of the wrist and carpometacarpal joints is less common in PsA.
C. Gout primarily affects the peripheral joints, typically the big toe, and can cause erosions, but not the specific pattern described in the question.
In summary, ankylosing spondylitis is the most suitable diagnosis due to its unique joint involvement pattern and the sparing of the wrist and carpometacarpal joints.
**Clinical Pearl:** The axial skeleton involvement in ankylosing spondylitis can lead to progressive spinal fusion, which may explain the patient's symptoms and physical examination findings.
**Why the Correct Answer is Right:**
Ankylosing spondylitis is a type of spondyloarthritis, a group of diseases characterized by inflammation and fusion of the axial skeleton, leading to chronic back pain and stiffness. While this condition primarily affects the spine, it can also cause involvement of the peripheral joints, including the PIP, DIP, and metacarpophalangeal joints. The pattern of joint involvement in the case described (sparing the wrist and carpometacarpal joints) is more consistent with ankylosing spondylitis than rheumatoid arthritis or psoriatic arthritis, which typically involve the wrist and carpometacarpal joints.
**Why Each Wrong Option is Incorrect:**
A. Rheumatoid arthritis (RA) typically affects the peripheral joints symmetrically, including the wrist and carpometacarpal joints,