Differential Diagnosis for Left Great Toe Pain

The patient's presentation of left great toe pain, erythema, and onset over the last 48 hours without a known injury warrants a thorough differential diagnosis. The following categories outline potential causes:

• Single Most Likely Diagnosis
  • Gout: This is a common condition characterized by sudden, severe attacks of pain, swelling, redness, and tenderness in one or more joints, most often the big toe. The patient's age, the location of the pain, and the acute onset are consistent with gout.
• Other Likely Diagnoses
  • Cellulitis: A bacterial skin infection that can cause redness, swelling, and pain. The absence of a known injury does not rule out cellulitis, as it can occur through minor, unnoticed breaks in the skin.
  • Osteoarthritis: While less likely to cause acute, severe pain without a history of chronic symptoms, osteoarthritis could contribute to an increased susceptibility to other conditions or could be exacerbated by another condition.
  • Trauma (including occult injury): Even without a remembered injury, minor trauma could have occurred, leading to pain and inflammation.
• Do Not Miss Diagnoses
  • Osteomyelitis: A bone infection that can present with pain, redness, and swelling. It is less common but critical to diagnose early due to the potential for serious complications.
  • Deep Vein Thrombosis (DVT): Although less common in the toes, DVT should be considered, especially if there are risk factors such as recent immobility, cancer, or coagulopathy.
  • Septic Arthritis: A joint infection that can cause severe pain, redness, and swelling. It is a medical emergency requiring prompt diagnosis and treatment.
• Rare Diagnoses
  • Pseudogout (Calcium Pyrophosphate Deposition Disease, CPPD): Similar to gout but caused by calcium pyrophosphate dihydrate crystals. It's less common and might be considered if gout is ruled out or if there are specific risk factors.
  • Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet. It could be primary or secondary to another condition like myeloproliferative disorders.
  • Complex Regional Pain Syndrome (CRPS): A condition characterized by persistent burning pain and inflammation following an injury, which could be minor and not recalled by the patient.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and potentially, diagnostic tests such as laboratory studies (e.g., uric acid levels, complete blood count), imaging (e.g., X-rays, ultrasound), and possibly arthrocentesis to analyze joint fluid.