This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
An 18 years old boy presents with digital gangrene in third and fouh finger for last 2 weeks. On examination the blood pressure is 170/110 mm of Hg and all peripheral pulses were palpable. Blood and urine examinations were unremarkable. Antinuclear antibodies, Antibody to double standard DNA and antineutrophil cytoplasmic antibody were negative. The most likely diagnosis is 
Select and explain. 
A. Wegner's granulomatosis, B. Polyaerltis nodosa, C. Takayasu's aeritis, D. Systemic lupus erythematosis (SLE)
B: Polyaerltis nodosa
Answer: B: Polyaerltis nodosa 
Explanation: The probable diagnosis is Polyaeritis nodosa Polyaeritis nodosa has a peak incidence between the ages of 40 and 50, with a male-to-female ratio of 2 : 1. The annual incidence is about 2/1 000 000. Hepatitis B is an impoant risk factor and the incidence is 10 times higher in the Inuit of Alaska, in whom hepatitis B infection is endemic. Presentation is with fever, myalgia, ahralgia and weight loss, in combination with manifestations of multisystem disease. The most common skin lesions are palpable purpura , ulceration, infarction and livedo reticularis . Pathological changes comprise necrotising inflammation and vessel occlusion, and in 70% of patients aeritis of the vasa nervorum leads to neuropathy, which is typically symmetrical and affects both sensory and motor function. Severe hypeension and/or renal impairment may occur due to multiple renal infarctions but glomerulonephritis is rare (in contrast to microscopic polyangiitis). The diagnosis is confirmed by conventional or magnetic resonance angiography, which shows multiple aneurysms and smooth narrowing of mesenteric, hepatic or renal systems, or by muscle or sural nerve biopsy, which reveals the histological changes described above. Treatment is with high-dose glucocoicoids and immunosuppressants, as described for ANCA-associated vasculitis . Ref - Davidsons 23e p1042