Case report of a nine-years old boy who was treated by the family practitioner for sinusitis, eye's papilla eďema and swelling of eyelids anď head. The CT examination did not confirmed the suspicious of intracranial tumor. The chest X-ray picture was not performed. After statement pseudotumor cerebri diagnosis the administration of dexamethason was started. The therapy was immediately followed with tumor lysis syndrome (metabolic disturbance with high level of urine acid and hyperkalemia and renal failure). The child was referred to the ICU of University Hospital with the diagnosis of hepatorenal failure. Before the transport the child was intubated and ventilated. At the ICU the immediate cardiopulmonary resuscitation was started but without any success. The pathologists revealed the mediastinal non-Hodgkin lymphoma at the autopsy.

        Key words: sudden death, non-Hodgkin lymphoma