Differential Diagnosis for Acute Onset Worsening Polyarticular Pain
Single Most Likely Diagnosis
- Methotrexate Withdrawal or Flare: The patient is already on methotrexate, and a sudden worsening of symptoms could be due to a flare of the underlying condition (e.g., juvenile idiopathic arthritis) or potentially due to issues with methotrexate adherence or effectiveness. The lack of erythema, swelling, and normal labs does not rule out a flare, especially in a patient with a known history of spondyloarthritis (sija) who might experience fluctuating symptoms.
Other Likely Diagnoses
- Illaris (Canakinumab) Efficacy Issues: Similar to methotrexate, issues with the efficacy of Canakinumab, an IL-1β inhibitor, could lead to a flare of the patient's condition, resulting in worsening polyarticular pain.
- Naproxen Tolerance or Inadequate Dosing: The patient might have developed tolerance to naproxen, or the current dosing might be inadequate to control the symptoms, leading to a perceived worsening of pain.
- Mechanical or Overuse Injury: Given the acute onset, it's possible that the patient has experienced a mechanical injury or overuse syndrome affecting multiple joints, which could present without significant swelling or erythema.
Do Not Miss Diagnoses
- Infection (e.g., Osteomyelitis, Septic Arthritis): Although labs are within normal limits and there's no erythema or swelling, it's crucial not to miss an infectious cause, especially in a patient on immunosuppressive therapy. Some infections can present atypically, and normal initial labs do not rule out infection entirely.
- Malignancy (e.g., Leukemia): Malignancies can cause bone and joint pain and must be considered, even though the presentation might not be typical and initial labs are normal. A high index of suspicion is required, especially if the pain is persistent and worsening.
Rare Diagnoses
- Seronegative Entropathic Arthropathy: A condition associated with inflammatory bowel disease, which could present with polyarticular pain without significant joint inflammation.
- Hypermobility Syndrome: Could be considered if the patient has a history of joint hypermobility and the pain is related to this condition.
- Neuropathic Pain Syndrome: Although less common, neuropathic pain syndromes can present with deep, aching pain that might be perceived as coming from the joints.