Vasculitis Quiz: Ace Your Exams

A 50-year-old man comes to the clinic due to fever, weight loss and weakness in his right foot and left hand for the past 2 months. During this period, he lost 4.5-kg (10-lb) without intention or changes in his diet. He has no jaw pain, change in vision, or headaches. He last visited his primary care physician more than 10 years ago, and his medical history is significant for IV drug use in his 20s. He no longer uses illicit drugs and does not smoke cigarettes. Temperature is 38.0°C (100.4° F), pulse is 80/min, and blood pressure is 145/90 mm Hg. Physical examination shows high-stepping gait when the patient lifts the right foot and decreased strength in the extensors of the left hand. There is no pain with palpation of the scalp. Cardiopulmonary exam shows no abnormalities. Skin examination shows purpura. Laboratory studies show the following:  

Laboratory value	Result
Hemoglobin	10 g/dL
Hematocrit	31%
Leukocyte count	15,000/mm3
Erythrocyte sedimentation rate	70 mm/h
C-reactive protein concentrations	30 mg/dL (N=0.08–3.1)
Serum
Hepatitis B surface antigen	Positive
Perinuclear anti-neutrophil cytoplasmic antibodies	Negative
Urine
Protein	2+
Erythrocytes	5-7/hpf
Creatinine	2.5 mg/dL

 
Which of the following is the most likely diagnosis?