A 3-year-old boy presented with constipation and perianal lesions resembling condyloma latum. The results of a biopsy of the perianal lesions confirmed the diagnosis of Langerhans cell histiocytosis (LCH). Although uncommon, LCH may involve the perianal region. In patients with functional constipation associated with perianal lesions that do not respond to conventional treatment, LCH should be part of the differential diagnosis. A simple biopsy of the external lesion and histologic examination of the mass are essential for diagnosis.