Gastrointestinal involvement in Langerhans cell histiocytosis (histiocytosis X): diagnosis by rectal biopsy.

We report two patients with biopsy-proven involvement of the gastrointestinal tract by Langerhans cell histiocytosis (LCH). The two patients were infants with congenital cutaneous lesions and bloody diarrhea beginning at 1 or 2 wk of age. Rectal biopsy specimens showed a mucosal infiltrate of typical Langerhans cells that focally invaded and destroyed the crypt epithelium. Gastrointestinal involvement by LCH is unusual and only rarely has represented a prominent clinical manifestation. In most cases, such involvement has been an indicator of widespread multisystemic disease. Its distinctive morphologic and immunohistochemical features allow LCH to be distinguished from other histiocytic infiltrations found in mucosal biopsy specimens.