A patient presented with pain in the hand. The joints involved were proximal interphalangeal joint, distal interphalangeal joint and first carpometacarpal joint. The wrist and metacarpophalangeal joints were spared. What is the likely diagnosis?

Correct Answer: D. Osteoarthritis

Osteoarthritis (OA) has a characteristic pattern of joint involvement that is the key discriminator here. OA preferentially affects the distal interphalangeal (DIP) joints, proximal interphalangeal (PIP) joints, and the first carpometacarpal (CMC) joint of the hand—exactly the pattern described. This distribution reflects the biomechanical stress on these high-mobility joints over time. The sparing of metacarpophalangeal (MCP) joints and wrist is pathognomonic for OA and helps exclude inflammatory arthropathies. In OA, cartilage degenerates due to mechanical wear and age-related changes, not immune-mediated inflammation. The DIP involvement with Heberden's nodes and PIP involvement with Bouchard's nodes are classic findings in hand OA, commonly seen in Indian women over 50 years. The first CMC joint is also frequently affected, causing thumb pain and functional impairment. This pattern is non-inflammatory in nature, with morning stiffness typically lasting <30 minutes. The diagnosis is confirmed by the absence of MCP involvement, which would suggest inflammatory arthritis like rheumatoid arthritis (RA). OA is the most common arthritis in India, particularly affecting weight-bearing joints and the hand in older populations.

Why the other options are wrong

A. Pseudogout — Pseudogout (calcium pyrophosphate deposition disease) presents with acute, episodic attacks of monoarticular or oligoarticular inflammation, typically affecting large joints like the knee, wrist, and shoulder. It does NOT show the chronic, symmetric, polyarticular pattern of DIP/PIP/CMC involvement described here. Pseudogout is acute and inflammatory; this patient has a chronic degenerative pattern. B. Rheumatoid arthritis — RA characteristically spares the DIP joints and preferentially affects MCP joints and wrists—the exact opposite of this case. RA is a symmetric, inflammatory polyarthritis with morning stiffness >1 hour, elevated inflammatory markers (ESR/CRP), and positive RF/anti-CCP. The sparing of MCP joints here excludes RA definitively. C. Psoriatic arthritis — Psoriatic arthritis can involve DIP joints (a feature that may seem similar), but it typically presents with asymmetric polyarthritis, dactylitis ('sausage digits'), and nail changes. It is inflammatory with elevated ESR/CRP and often occurs in patients with psoriatic skin lesions. The symmetric, non-inflammatory pattern of OA with isolated DIP/PIP/CMC involvement is not typical of psoriatic arthritis.

High-Yield Facts

Mnemonics

Hand OA Pattern: DIP-PIP-CMC (Not MCP) DIP, PIP, CMC = OA. MCP = Inflammatory (RA, PsA). Remember: OA avoids the MCP joint; inflammatory arthritis loves it. Heberden & Bouchard = Hand OA Heberden (DIP nodes) and Bouchard (PIP nodes) = Hand Bones in OA. Visual memory: bumpy fingers in older patients = OA.

NBE Trap

NBE may expect students to confuse DIP involvement across multiple arthropathies. However, the combination of DIP + PIP + CMC with MCP sparing is unique to OA. Students who know only that "psoriatic arthritis can affect DIP" may incorrectly choose option C without recognizing the inflammatory pattern and MCP involvement typical of PsA.

Clinical Pearl

In Indian primary care, hand OA is the most common arthritis in women >50 years, often presenting with thumb CMC pain affecting grip strength and daily activities like grinding spices. The absence of morning stiffness and negative inflammatory markers help confirm OA and avoid unnecessary immunosuppressive therapy.

_Reference: Robbins Ch. 26 (Osteoarthritis); Harrison Ch. 313 (Osteoarthritis of the Hand)_