Differential Diagnosis for a White Patch of Skin on the Lower Leg

• Single most likely diagnosis
  • Vitiligo: This is a condition characterized by the loss of skin pigment cells, leading to white patches. It can occur anywhere on the body, including the lower leg, and is often associated with autoimmune diseases.
• Other Likely diagnoses
  • Tinea versicolor: A fungal infection that can cause patches of discolored skin, including white patches, especially in areas with high sebaceous gland activity.
  • Pityriasis alba: A mild skin condition causing small patches of light skin, often on the face but can occur on the legs, typically seen in children and associated with eczema.
  • Post-inflammatory hypopigmentation: This can occur after skin inflammation or injury, leading to areas of lighter skin.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignant melanoma (with regression): In rare cases, a melanoma can regress, leaving behind a white or hypopigmented patch. Early detection is crucial for treatment.
  • Sarcoidosis: A condition that can cause skin lesions, including hypopigmented patches, and can affect multiple organs, requiring prompt diagnosis and treatment.
• Rare diagnoses
  • Piebaldism: A rare genetic condition characterized by the absence of melanocytes in affected areas of skin and hair, leading to white patches and often hair loss.
  • Waardenburg syndrome: Another genetic disorder that affects the development of melanocytes, leading to patches of hypopigmentation among other symptoms.
  • Idiopathic guttate hypomelanosis: A condition of unknown cause, characterized by small, discrete, hypopigmented macules, often on the legs.