An Uncommon Case of Lichen Spinulosus in an Adult Patient Clinically Mmimicking Folliculotropic Mycosis Fungoides.

Lichen spinulosus (LS) is an uncommon skin condition mostly in children and adolescents but uncommon in adults. It presents as a group of hypopigmented or skin-colored follicular papules and keratotic spines with a sandpaper-like appearance. There is a lymphohistiocytic infiltrate in the dermis centered around hair follicles. We present a rare case of LS in a 52-year-old woman with a rough, bumpy, itchy rash affecting the trunk and extremities. Her rash consisted of clusters of hyperkeratotic follicular-based spiny papules. Histologic sections demonstrated several dilated hair follicles filled with keratotic plugs surrounded by a dense perifollicular lymphohistiocytic infiltrate, particularly at the level of the infundibula, that extended into the follicular epithelium.