Late‐onset self‐healing reticulohistiocytosis: Pediatric case of Hashimoto–Pritzker type Langerhans cell histiocytosis

ABSTRACT An 8‐year‐old otherwise healthy girl presented with a 3‐month history of multiple asymptomatic, reddish‐brown papules over the face and upper limbs. Histopathological and immunohistochemical examinations demonstrated an infiltrate of mononuclear cells containing abundant histiocytic cells in the dermis, and microabscess‐like accumulation of the histiocytic cells in the epidermis. The histiocytic cells were positive for antibodies against S‐100 protein and CD1a, but negative for anti‐CD68. Lag and anti‐langerin monoclonal antibodies reacted more weakly with these histiocytic cells than with Langerhans cells in the surrounding epidermis. The skin lesions spontaneously regressed within the following 3 months, and neither systemic involvement nor local recurrence was observed during the next 10 months. This case should be categorized as congenital self‐healing reticulohistiocytosis (Hashimoto–Pritzker), although the onset was not early in life.