Differential Diagnosis for Itchy Rash to Outer Labia

• Single most likely diagnosis
  • Eczema/Dermatitis: This is a common condition that can cause itchy rashes on the outer labia due to irritation, allergic reactions, or atopic dermatitis.
• Other Likely diagnoses
  • Contact dermatitis: This could be due to irritants such as soaps, dyes in clothing, or other products that come into contact with the skin.
  • Lichen sclerosus: A condition that creates patchy, white skin that's thinner than normal, often itchy and painful, commonly affecting the genital and anal areas.
  • Lichen planus: An inflammatory condition that affects mucous membranes inside the mouth and other areas of the body, including the genital area, causing an itchy, painful rash.
  • Psoriasis: Although less common in the genital area, psoriasis can cause itchy, scaly patches.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Herpes simplex virus (HSV): While often associated with painful blisters, HSV can also cause itching before the onset of visible lesions.
  • Syphilis: The secondary stage of syphilis can cause a rash that might be itchy, and it's crucial to diagnose and treat syphilis to prevent long-term complications.
  • Vulvar intraepithelial neoplasia (VIN) or cancer: Although rare, any persistent or unusual rash should be evaluated for the possibility of VIN or vulvar cancer, especially in older women or those with a history of HPV.
• Rare diagnoses
  • Zoon's vulvitis: A rare condition characterized by a well-demarcated, erythematous plaque on the vulva, often associated with itching and burning.
  • Extramammary Paget's disease: A rare skin condition that can cause an itchy, eczema-like rash in the vulvar area, associated with an underlying adenocarcinoma.
  • Lichen simplex chronicus: A condition resulting from prolonged scratching of the skin, leading to thickening and hyperpigmentation, which can be itchy.