Differential Diagnosis

The patient presents with bilateral distal and proximal phalangeal joints pain with nodules, no morning stiffness, normal C-reactive protein (CRP), and normal rheumatoid factor (RF). Based on these symptoms, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • D. Osteoarthritis (OA): The presence of nodules, particularly if they are Heberden's (distal interphalangeal joints) or Bouchard's nodes (proximal interphalangeal joints), is highly suggestive of OA. The lack of morning stiffness and normal inflammatory markers (CRP and RF) also support this diagnosis, as OA is typically a non-inflammatory condition.

• Other Likely Diagnoses

  • A. Polyarticular Gout: Although gout can present with acute, episodic joint pain and normal inflammatory markers between episodes, the presence of nodules (which could be tophi in gout) and the involvement of multiple small joints could suggest polyarticular gout. However, the absence of a history of acute, severely painful monoarthritis episodes makes this less likely.
  • B. Reactive Arthritis: This condition usually follows a gastrointestinal or genitourinary infection and is characterized by asymmetric oligoarthritis, predominantly affecting the lower limbs. The patient's symptoms do not strongly suggest reactive arthritis, especially given the bilateral and symmetric involvement of the hands.

• Do Not Miss Diagnoses

  • C. Rheumatoid Arthritis (RA): Although the patient has normal RF and no morning stiffness, which are common features of RA, it is crucial not to miss this diagnosis. Some patients with RA can have a seronegative status (normal RF and anti-CCP antibodies), and morning stiffness can be variable. However, the presence of nodules and the specific joint involvement pattern might be more typical of OA. Still, RA should be considered, especially if there are other systemic symptoms or if the clinical picture evolves.

• Rare Diagnoses

  • Psoriatic Arthritis (PsA): This condition can present with a variety of manifestations, including asymmetric oligoarthritis, distal interphalangeal joint predominant arthritis, and the presence of dactylitis or enthesitis. While nodules could be seen in the form of psoriatic skin lesions, the primary description provided does not strongly suggest PsA, especially without mention of skin or nail changes.
  • Other rare conditions such as multicentric reticulohistiocytosis or rheumatoid nodulosis could present with nodules and joint pain but are much less common and would typically have additional distinguishing features.