Abstract: Objectives To report the first case of multiple trichodis coma in China.A 31-year-old man presented with multiple,broomcorn graintored bean-sized,skin-colored,firm papules on the right lower extremity for 15 years,and similar lesions on the left knee and lower leg for about one year.The lesions were asymptomatic. Methods and Results Histopathology showed acanthosis of epidermis,proliferation of fine reticulate collagen fibers and depositi on of focal mucinous proteins in upper dermis.Small blood vessels and nerve fib ers were increased,and proliferation of elastic fibers was localized in the hair follicles and around some reteridges.Proliferated hair follicles were seen in the margins of the lesions and extended down in a collar-like pattern.Ultra structurally,Merkel cell-axon complex was located in the overlying basallamina of the epidermis.Myelinated nerve fibers were seen in the upper dermis.Blood vessel alterations were found under electron microscopy,some basal laminae of blood vessels exhibited laminated structure,proliferation of fibrous component,and thickened wall of blood vessels were observed. Conclusions The disease is rare.It is a hamartomaoriginated from hair disk.

Key words: Trichodiscoma, Hair disc, Merkel cells, Neurites