RESUMEN
A 51-year-old man was referred by his dentist to a maxillofacial surgeon with complaints of illness and pain in the mandible, associated with a rapidly expanding area of black gingiva and mucosa surrounding the lower front teeth. Clinically and radiographically there was evidence of an infected necrosis of the chin and floor of mouth. Following debridement at the operating room, the patient was treated at the intensive care unit for septic shock leading to prolonged hospitalisation. Investigation of the bone marrow did not provide an explanation for pancytopenia or the severity of the illness. In addition, genetic investigation of thiopurine S-methyltransferase gene showed no mutations. This gene codes for an identically named protein enzyme that contributes in the metabolising of the medicine azathioprine, used daily for an autoimmune disease. A combination of the use of azathioprine, a folic acid deficiency and sepsis led to this exceptional course of illness. Therapeutic intervention consisted of surgical debridement and treatment of the bacteraemia. Afterwards several corrective surgeries were necessary to restore oral functions.