Differential Diagnosis for Rheumatoid Arthritis

When considering a differential diagnosis for rheumatoid arthritis (RA), it's crucial to evaluate a range of conditions that can mimic its symptoms. The differential can be categorized as follows:

• Single Most Likely Diagnosis
  • Osteoarthritis (OA): Often considered in the differential due to its high prevalence and similar presentation of joint pain and stiffness, although the pattern of joint involvement and presence of systemic symptoms can help distinguish it from RA.
• Other Likely Diagnoses
  • Psoriatic Arthritis (PsA): Characterized by psoriatic skin lesions and specific types of joint involvement, which can sometimes be confused with RA, especially in the absence of clear psoriatic lesions.
  • Lupus: Systemic lupus erythematosus can present with joint pain and swelling similar to RA, along with other systemic symptoms such as skin rashes and kidney issues.
  • Spondyloarthritis: Including conditions like ankylosing spondylitis, which primarily affects the spine but can also involve peripheral joints, sometimes mimicking RA.
• Do Not Miss Diagnoses
  • Septic Arthritis: An infection within a joint, which is a medical emergency requiring prompt diagnosis and treatment to prevent joint destruction and systemic complications.
  • Gout or Pseudogout: Acute crystal-induced arthropathies that can cause sudden, severe joint pain and swelling, often involving a single joint initially, which must be distinguished from RA due to different treatment approaches.
  • Lyme Disease: Caused by a tick-borne infection, can lead to arthritis that might be mistaken for RA, especially if the characteristic rash is not present or recognized.
• Rare Diagnoses
  • Relapsing Polychondritis: A rare autoimmune disorder that can cause cartilage inflammation, leading to joint pain and other systemic symptoms that might be confused with RA.
  • Adult-Onset Still's Disease: A rare condition characterized by high fevers, salmon-colored rash, and joint pain, which can be mistaken for RA or other autoimmune diseases due to its systemic nature.
  • Hemochromatosis: A genetic disorder leading to iron overload, which can cause arthropathy among other systemic symptoms, and might be considered in the differential for RA, especially if there are other signs of iron overload.

Each of these conditions has distinct features that can help in differentiating them from rheumatoid arthritis, emphasizing the importance of a thorough clinical evaluation, laboratory tests, and sometimes imaging studies to reach an accurate diagnosis.