Differential Diagnosis
- Single most likely diagnosis
- C. Psoriasis arthritis: The patient is a known case of psoriasis and presents with multiple joint pain (right big toe, right ankle, and bilateral knee pain) which is not typical for gout. Psoriatic arthritis often presents with oligoarthritis or polyarthritis, and the patient's lack of response to allopurinol (a medication primarily used for gout) suggests that the current symptoms may not be due to gout.
- Other Likely diagnoses
- B. Active gout arthritis: Although the patient was initially diagnosed with gout and is on allopurinol, the presence of high uric acid levels and the recurrence of symptoms could suggest active gout, especially if the allopurinol dose is not adequate or if the patient is not adherent to the medication.
- A. Active pseudo-gout arthritis: This condition, also known as calcium pyrophosphate deposition disease (CPPD), can present similarly to gout and may not respond to allopurinol. However, it typically affects larger joints like the knees.
- Do Not Miss
- Septic arthritis: Although less likely given the context, septic arthritis is a medical emergency that requires prompt diagnosis and treatment. The presence of multiple joint pain and the lack of response to initial treatment could potentially suggest an infectious process, especially if there are systemic symptoms like fever.
- Rare diagnoses
- Other rheumatologic conditions: Conditions like rheumatoid arthritis, although less likely given the patient's history of psoriasis and initial diagnosis of gout, could present with similar symptoms. However, these would be less common given the specific pattern of joint involvement and the patient's known history.