Differential Diagnosis for 80-year-old Male with Acute Erythema, Swelling, and Pain around Left Thumb

• Single most likely diagnosis:
  • Gout: Given the patient's history of chronic kidney disease (CKD) and the acute onset of erythema, swelling, and pain around the left thumb without recent trauma, gout is a highly plausible diagnosis. CKD can lead to elevated uric acid levels, increasing the risk of gout. The involvement of the thumb, a common site for gouty attacks, further supports this diagnosis.
• Other Likely diagnoses:
  • Pseudogout (Calcium Pyrophosphate Deposition Disease, CPPD): Similar to gout, pseudogout can cause acute, painful swelling of joints, including those in the hands. The patient's age and history of "arthritis" could suggest a predisposition to CPPD.
  • Septic Arthritis: Although the patient reports no recent trauma or open wounds, septic arthritis is a consideration, especially in the elderly, due to its potential for severe consequences if not promptly treated. Bacterial infection can cause acute joint pain and swelling.
  • Cellulitis: This is an infection of the skin and subcutaneous tissues that could present with erythema, swelling, and pain. The absence of open wounds does not rule out cellulitis, as it can occur without an obvious source of infection.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Necrotizing Fasciitis: A severe infection that can rapidly progress and has a high mortality rate if not promptly recognized and treated. The presence of severe pain out of proportion to the physical findings and signs of skin necrosis should raise suspicion.
  • Osteomyelitis: An infection of the bone that can occur without an obvious source of infection. It requires prompt diagnosis and treatment to prevent serious complications.
• Rare diagnoses:
  • Rheumatoid Arthritis (RA) Flare: Although the patient has a history of "arthritis," a flare of RA could present with acute symptoms. However, the involvement of a single joint and the absence of other systemic symptoms make this less likely.
  • Sarcoidosis: A systemic disease that can cause arthritis among other symptoms. It is less common and would be considered if other diagnoses are ruled out and there are systemic symptoms or findings suggestive of sarcoidosis.
  • Tumor or Cancer: A tumor or cancer affecting the bone or soft tissue around the thumb could cause pain and swelling. This would be an unusual presentation but should be considered if initial evaluations do not reveal a more common cause.