Differential Diagnosis for Skin Darkening of Medial Ankles

• Single most likely diagnosis
  • Eczema (atopic dermatitis) or contact dermatitis: This is a common condition that can cause skin darkening and thickening, especially in areas prone to friction or irritation, such as the medial ankles.
• Other Likely diagnoses
  • Dry skin (xerosis): Prolonged dryness can lead to darkening and thickening of the skin, particularly in areas subject to increased friction.
  • Friction or pressure-induced hyperpigmentation: Repeated friction or pressure on the skin can cause darkening due to inflammation and subsequent hyperpigmentation.
  • Stasis dermatitis: This condition occurs due to poor circulation, leading to fluid buildup and skin changes, including darkening, often seen in the lower legs.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Malignancy (e.g., acral lentiginous melanoma): Although rare, skin darkening could be a sign of a malignant process, making it crucial to consider and rule out.
  • Sickle cell disease or other hemoglobinopathies: These conditions can lead to skin changes, including darkening, due to chronic hemolysis and tissue damage.
  • Chronic venous insufficiency: This condition can lead to significant skin changes, including darkening and ulceration, due to poor blood circulation.
• Rare diagnoses
  • Erythema ab igne: A condition caused by prolonged exposure to heat, leading to reticulated hyperpigmentation.
  • Fixed drug eruption: A type of drug reaction that can cause well-defined areas of skin darkening.
  • Hemochromatosis: A genetic disorder leading to iron overload, which can cause skin darkening among other systemic symptoms.
  • Addison's disease: A rare endocrine disorder characterized by adrenal insufficiency, which can lead to generalized skin darkening.