A 28 y.o. patient complains of pain in legs during walking, chill of feet and toes. He has been ill for a year. Objectively: leg skin is pale, cool; turgor is decreased, hypotrichosis. Femoral and popliteal artery pulsation is weak, it is palpable on the foot arteries only after nitroglycerine test. Rheographic index is <1. What is the most probable diagnosis?