We report a case of a 43-year-old man, previously healthy, with a three-month history of weight loss, dyspnea, cough, hemoptysis and chest pain, followed by polyuria and polydipsia during the last weeks. Clinical investigation disclosed diabetic ketoacidosis, pulmonary tuberculosis and pneumomediastinum. The patient’s outcome was favorable after clinical treatment and the pneumomediastinum resolved spontaneously without specific intervention.