Differential Diagnosis for Well-Circumscribed Pink Patches on Scalp

• Single Most Likely Diagnosis
  • Seborrheic dermatitis: This condition is characterized by well-circumscribed, pink to yellowish patches, often found on the scalp. It's a common condition and the presentation matches closely.
• Other Likely Diagnoses
  • Psoriasis: While psoriasis can present with more scaly, erythematous plaques, some forms, especially on the scalp, can appear as well-circumscribed pink patches.
  • Tinea capitis (ringworm of the scalp): This fungal infection can cause patches that are well-circumscribed and may appear pink, especially in the early stages.
  • Alopecia areata: Though primarily known for causing hair loss, some forms of alopecia areata can present with erythematous patches.
• Do Not Miss Diagnoses
  • Cutaneous T-cell lymphoma (Mycosis fungoides): Although rare, this condition can present with patches or plaques that are similar in appearance to benign conditions. Missing this diagnosis could have severe consequences.
  • Secondary syphilis: This condition can cause a wide range of skin manifestations, including patches on the scalp. It's crucial to consider syphilis due to its potential for serious complications if left untreated.
• Rare Diagnoses
  • Pityriasis rubra pilaris: A rare skin disorder that can cause well-circumscribed, orange-pink patches, among other symptoms.
  • Lichen planopilaris: An autoimmune condition that can lead to hair loss and may present with erythematous, well-circumscribed patches on the scalp.
  • Discoid lupus erythematosus: A chronic skin condition of sores with inflammation and scarring favoring the face, ears, and scalp but can be considered in the differential for well-circumscribed pink patches.