Obstructive sleep apnea syndrome (OSAS) has severe, life-threatening complications such as hypertension, stoke, ischemic heart disease or rhythm problems. A 40-year old woman was referred to our sleep laboratory due to witnessed apnea during her hospitalization in endocrinology yard because of hypertension, hipophyseal microadenoma and Cushing syndrome. Her past medical history revealed that she had snoring, sweating at night, tiredness in morning and excessive daytime sleepiness for the last 10 years. In polysomnography investigation, we observed continuous obstructive hypopneas during NREM sleep stage with an index of 60 (times per an hour). As she started to have REM sleep stage, she had a central apnea lasting for 100 seconds, followed by bradicardia and cardiac arrest; the patient was lost in spite of urgent intervention. Here we aimed to attract attention of physicians from all disciplines to OSAS, which is a neurological life-threatening condition but all complications could be removed by non-invasive mechanical ventilation therapy. Especially in the presence of hypertension, obesity and cardiac disorders, OSAS should be questioned in detailed and be treated immediately. Otherwise, delay in diagnosis and treatment would result in lethal consequences, as in the patient reported here.