Differential Diagnosis for Osteoarthritis and Rheumatoid Arthritis of the Hand

When differentiating between osteoarthritis (OA) and rheumatoid arthritis (RA) of the hand, it's crucial to consider various factors including symptoms, physical examination findings, and diagnostic tests. Here's a structured approach to the differential diagnosis:

• Single Most Likely Diagnosis
  • Osteoarthritis (OA): This is often the most likely diagnosis in older adults presenting with gradual onset of pain and stiffness in the hands, particularly affecting the distal interphalangeal joints (DIP) and the base of the thumb. OA is characterized by joint space narrowing, subchondral sclerosis, and osteophyte formation on radiographs.
• Other Likely Diagnoses
  • Rheumatoid Arthritis (RA): RA is an autoimmune disorder that can cause symmetric polyarthritis, often affecting the metacarpophalangeal joints (MCP) and proximal interphalangeal joints (PIP) of the hands. Morning stiffness lasting more than an hour, systemic symptoms, and specific autoantibodies (like RF or anti-CCP) support this diagnosis.
  • Psoriatic Arthritis (PsA): This condition can mimic both OA and RA but is distinguished by the presence of psoriasis, dactylitis (sausage fingers), and characteristic radiographic findings such as pencil-in-cup deformities.
• Do Not Miss Diagnoses
  • Septic Arthritis: Although less common, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. It presents with acute onset of pain, swelling, and decreased range of motion in a single joint, often accompanied by systemic signs of infection like fever.
  • Gout: Gouty arthritis can affect the hands, particularly the DIP joints, and is characterized by sudden onset of intense pain, redness, and swelling. Urate crystals in the joint fluid are diagnostic.
  • Lupus: Systemic lupus erythematosus (SLE) can cause hand arthritis that may resemble RA, but it is distinguished by other systemic manifestations and specific autoantibodies.
• Rare Diagnoses
  • Hemochromatosis: This genetic disorder leads to iron overload and can cause a type of arthritis that resembles OA, particularly affecting the second and third metacarpophalangeal joints.
  • Sarcoidosis: Sarcoid arthritis can affect the hands and is part of a systemic disease characterized by granulomatous inflammation in various organs.
  • Relapsing Polychondritis: A rare autoimmune disorder that can cause cartilage inflammation, including that in the joints of the hands, leading to pain, swelling, and eventually deformity.

Each of these diagnoses has distinct clinical and radiological features that guide the differential diagnosis. A thorough history, physical examination, laboratory tests, and imaging studies are essential for accurate diagnosis and appropriate management.