Histiocytic disorders with spontaneous regression in infancy.

The histiocytic disorders are uncommon, have a wide spectrum, and are poorly understood. We describe seven cases developing in infancy, seen during a period of 9 years at Asan Medical Center, Seoul, Korea. Clinically the patients had multiple papules over the face, trunk, and extremities that developed at birth or during infancy. Histopathologic examinations revealed an infiltrate of many histiocytic cells in the upper dermis with or without epidermotropism. Four cases were classified as congenital self-healing reticulohistiocytosis in that the histiocytes were identified as Langerhans cells by positive immunohistochemical staining for S-100 protein, ultrastructural studies showing many Birbeck granules, and spontaneous regression of the lesions within 1-4 months. One infant with a solitary lesion on the forehead was diagnosed as solitary, congenital, indeterminate cell histiocytoma because the histiocytic cells were S-100 protein positive, but meticulous ultrastructural studies did not detect Birbeck granules. The lesion was removed by shave excision. Two cases were classified as generalized eruptive histiocytoma. The histiocytic cells were S-100 protein negative and ultrastructurally Birbeck granules were absent. In one patient, eyeball- or popcornlike lysosomal structures were seen. The lesions regressed completely.