Diagnosis of acute porphyria is a difficult clinical task because there are no any specific symptoms of this disease. The triad of symptoms usually characterizes acute porphyria: visceral abdominal pain, neurologic dysfunction and mental disorders. It is difficult to distinguish neuropathy caused by porphyria from other forms of nervous system lesion, for example Guillain-Barre syndrome. Typical laboratory signs of disease are resistant hyponatremia and change of urine color. However, initially suspected attack of acute porphyria should be confirmed by multiple non-specific clinical signs and subsequent laboratory tests. The last ones are not available routinely in general clinical practice as a rule. Final diagnosis and pathogenetic therapy are usually carried out in hematological clinics. Clinical case of the young man with abdominal pain and polyneuropathy consecutively examined and treated in three different hospitals with three different diagnoses within a month is presented in the article. Treatment of «post intensive care syndrome» (PICS) in this patient has led to manifestation of porphyria that has allowed to make a correct diagnosis.