Case of Follicular Mucinosis: Nestin-Expression in Mucin-Producing Cells

A 29-year-old Japanese man presented with a solitary, indurated, erythematous plaque on his jaw, which had been present for a month and exhibited follicular hyperkeratosis and hair loss. A skin biopsy revealed dense perifollicular lymphocytic infiltration with eosinophils and reticular epithelial degeneration in hair follicles and sebaceous glands due to mucoid material. The mucoid material stained with Alcian blue at pH 2.5, confirming follicular mucinosis. Immunohistochemistry showed that the degenerated outer root sheath cells were nestin-positive and keratin 15-negative, indicating they originated from nestin-positive, multipotent hair follicle stem cells.