Differential Diagnosis for Dark Patch in Groin

• Single most likely diagnosis
  • Tinea cruris (jock itch): This is a common fungal infection in the groin area, characterized by a dark, itchy patch. It's prevalent in warm, moist environments and is often seen in individuals who engage in sports or wear tight clothing.
• Other Likely diagnoses
  • Eczema (atopic dermatitis or contact dermatitis): Eczema can cause dark, itchy patches in the groin area due to inflammation and skin irritation.
  • Intertrigo: This is a skin condition caused by friction and moisture, leading to red, brown, or black patches in skin folds, including the groin.
  • Melasma: Although more common on the face, melasma can occasionally appear in other areas, including the groin, causing dark patches due to hormonal changes or sun exposure.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
  • Malignant melanoma: Although rare, a new, dark patch in the groin could potentially be a sign of skin cancer, including malignant melanoma, which requires prompt medical attention.
  • Lymphoma: Certain types of lymphoma can cause skin lesions or patches, including in the groin area.
• Rare diagnoses
  • Fixed drug eruption: A rare condition where certain medications cause skin lesions or patches, including in the groin area, upon re-exposure to the drug.
  • Pigmented contact dermatitis: A condition where the skin becomes darkened due to an allergic reaction to certain substances coming into contact with the skin.
  • Hemochromatosis: A genetic disorder leading to iron overload, which can cause skin darkening (bronze diabetes), although this would be a more generalized condition rather than localized to the groin.