Differential Diagnosis for Hypopigmented Rash around Anus in a 50-year-old Woman with Pruritis

• Single most likely diagnosis
  • Lichen sclerosus: This condition is characterized by thin, white, patchy skin that is easily torn and can cause significant pruritis. It often affects the genital and anal areas and is more common in women.
• Other Likely diagnoses
  • Psoriasis: Although typically associated with red, scaly plaques, inverse psoriasis can present as smooth, red, and shiny patches in intertriginous areas, including the perianal region, and can cause pruritis.
  • Contact dermatitis: Irritant or allergic contact dermatitis can cause a rash around the anus, especially if the patient uses certain soaps, wipes, or topical treatments that irritate the skin.
  • Lichen planus: This is an inflammatory condition that can affect the skin and mucous membranes, leading to purplish, itchy, flat bumps. It can involve the perianal area and cause significant discomfort.
• Do Not Miss diagnoses
  • Extramammary Paget's disease: A rare skin malignancy that can present as a persistent, pruritic rash in the anogenital area. Early diagnosis is crucial for effective treatment.
  • Bowen's disease (intraepithelial neoplasia): A form of skin cancer that can appear as a slow-growing, pigmented or hypopigmented lesion in the perianal area.
• Rare diagnoses
  • Vitiligo: An autoimmune condition leading to loss of pigment-producing cells, resulting in white patches. While it can occur anywhere, including the perianal area, it's less common in this location compared to other areas of the body.
  • Scleroderma: A chronic disease characterized by deposition of collagen, leading to hardening and tightening of skin and connective tissue. It can cause skin changes, including hypopigmentation, but perianal involvement is rare.