Congenital insensitivity to pain with anhidrosis is a rare disorder. Its primary clinical features include congenital analgesia, which leads to self-mutilation; inability to sweat, which leads to defective thermoregulation; and mental retardation. A five-year-old boy with consanguineous parents and no family history of the disorder presented with ulcerating lesions on both knees and elbows. His family had discovered the lack of sensation to pain and anhidrosis. Physical examination revealed ulcers on both knees and elbow, self-mutilation of the tongue, fingers, and toes. Sensation to touch was intact and lacrimation was normal. Moderate mental retardation and analgesia were noted in an otherwise normal neurologic examination. The results of electromyographic examination were normal and the application of pilocarpine showed anhidrosis. A skin biopsy specimen was also examined.