Self Injurious Behaviour (SIB) is a deliberate harm to the body that may lead to factitial injuries. Its origin may be functional or biological and it has a higher prevalence in females and in psychologically impaired individuals. Seventy per cent of autistic patients have SIB. Seventy-five per cent of factitial injuries are located in the head and neck region. A paediatric case report concerning a 4-year-old autistic female is presented. Detailed medical history, physical examination, clinical intraoral and radiographic examination, incisional biopsy, neuropaediatrical, psychological and speech evaluation were undertaken. Diagnosis included hypochromic macrocytic anaemia, caries, coronal fracture, factitial ulcer, factitial periodontitis, self-extraction of primary teeth and permanent teeth buds, non-specific oral ulcer with inflammatory reaction, mild mental retardation, speech impairment, autistic syndrome and self injurious behaviour consisting of putting fingers and foreign objects in the gingiva, fingernail biting and hair pulling. Differential diagnosis included hystiocitosis X, prepuberal periodontitis and leukocyte adhesion deficiency. Dental preventive and restorative treatment was performed. Non-contingent reinforcement therapy was successfully used to diminish SIB. Treatment of factitial oral injuries must be interdisciplinary and requires cooperation of the patient, the parents, health care providers, and medical team.