A previously healthy 40-year-old Japanese male was urgently admitted with a 2-month history of dysphagia, 30-kg weight loss, and fever. Human immunodeficiency virus (HIV) antibodies and cytomegalovirus antigenemia were positive. Pneumocystis pneumonia and cytomegalovirus pneumonia were suspected. The patient was diagnosed with acquired immune deficiency syndrome (AIDS). Cytomegalovirus antigenemia became negative 20 days after the positive result. On hospital day 41, he experienced cardiopulmonary arrest. The clinical diagnosis was fulminant type 1 diabetes mellitus. He later developed hypoglycemia and was diagnosed with adrenal insufficiency accompanied by septic shock. He died of multiple organ failure 29 h post-admission to our ICU.