[Syncope of undetermined origin].

A 48-year-old man with no significant medical history suddenly suffered, when walking, a sensation of thoracic pressure and severe dyspnea, soon followed by loss of consciousness without seizure. On hospitalization the following abnormal features were found: moderate cyanosis and cutaneous erythematous lesions; a blood gas analysis with moderate hypoxemia and slight compensated metabolic acidosis; and on chest X-ray a small band of atelectasis of the left lower lobe. An ECG, a continuous 24 hours Holter ECG recording and pulmonary scintigraphy were within normal limits. During the next few days the patient had several syncopal attacks without detectable cause. Two biopsies were then performed which established the diagnosis.