Differential Diagnosis for 67 year old male with redness of left foot

• Single most likely diagnosis
  • Cellulitis: Given the patient's history of cellulitis on the elbow and the recent trauma to the foot, cellulitis is a likely diagnosis. The increasing pain and redness since the injury also support this diagnosis.
• Other Likely diagnoses
  • Infected traumatic wound: The patient's history of bumping his foot on a chair leg and the subsequent increase in pain and redness suggest a possible infected wound.
  • Diabetic foot infection: Although the patient's A1C is well-controlled, his history of diabetes mellitus (DM) puts him at risk for foot infections, especially given the recent trauma.
  • MRSA infection: The patient's history of MRSA infection increases the likelihood of another MRSA infection, especially in the context of a traumatic wound.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Osteomyelitis: Although less likely, osteomyelitis is a serious condition that can occur in diabetic patients or those with a history of trauma. It would be deadly if missed due to the risk of sepsis and amputation.
  • Necrotizing fasciitis: This is a rare but life-threatening condition that can occur after trauma. It is essential to consider this diagnosis, especially given the patient's history of MRSA and cellulitis.
  • Deep vein thrombosis (DVT): Although the patient's symptoms are localized to the foot, DVT is a possible diagnosis that could be deadly if missed due to the risk of pulmonary embolism.
• Rare diagnoses
  • Erythema nodosum: This is an inflammatory condition that can cause redness and pain in the affected area. Although rare, it is essential to consider this diagnosis, especially if the patient's symptoms do not respond to typical treatments for cellulitis or infected wounds.
  • Gout or pseudogout: These conditions can cause sudden onset of pain and redness in the foot, although they are less likely given the patient's history of trauma.