A 30 year old male presents with numbness of both lower limbs and right upper limb. Examination reveals pulse 88/minutes and BPI 160/110 mm of Hg. He also has digital gangrene involving right 2nd and 3rd finger, urine routine examination is unremarkable. Microscopic examination shows RBC's. Hemogram and serum biochemistry is within normal limits. What is the most probable diagnosis?