Differential Diagnosis for Purple Leg

The differential diagnosis for a purple leg can be organized into the following categories:

• Single Most Likely Diagnosis
  • Deep Vein Thrombosis (DVT): This is a common condition where a blood clot forms in the deep veins of the leg, causing swelling, pain, and discoloration, which can appear as purple.
• Other Likely Diagnoses
  • Cellulitis: A bacterial skin infection that can cause redness, swelling, and warmth of the skin, which may appear purple in severe cases.
  • Varicose Veins: Enlarged veins that can cause skin discoloration, including a purple hue, due to poor blood circulation.
  • Trauma: Injury to the leg can cause bruising, which may appear as purple discoloration.
• Do Not Miss Diagnoses
  • Compartment Syndrome: A serious condition where increased pressure within the muscle compartments of the leg can lead to nerve and muscle damage, often presenting with severe pain, swelling, and discoloration.
  • Pulmonary Embolism (if DVT is suspected): A life-threatening condition where a blood clot breaks loose and travels to the lungs, requiring immediate medical attention.
  • Sepsis (if cellulitis is suspected): A potentially life-threatening condition that occurs when the body's response to an infection becomes uncontrolled and causes widespread inflammation.
• Rare Diagnoses
  • Lymphoma: A type of cancer that can cause skin discoloration, including purple lesions, although this is a rare presentation.
  • Kaposi's Sarcoma: A rare cancer that can cause purple lesions on the skin, often associated with immune system dysfunction.
  • Vasculitis: Inflammation of the blood vessels, which can cause skin discoloration, including purple, although this is a rare condition.

Each diagnosis has a brief justification based on common causes of purple leg discoloration, with an emphasis on not missing potentially life-threatening conditions.