AB0514 CALF PAIN, KEY POINT IN THE DIAGNOSIS OF POLYARTERITIS NODOSA

Background: polyarteritis nodosa (PAN) is a primary systemic vasculitis that is becoming a rare disease in part by the decrease in hepatitis B virus (HBV) infection due to widespread vaccination. It is characterized by a full vast constellation of nonspecific clinical manifestations, which sometimes delays and makes it difficult to diagnose. Still, muscle involvement is a feature that could guide the clinician. Objectives: to describe the main clinical and laboratory characteristics of patients with PAN and to confirm the frequency of muscle involvement. Methods: retrospective cross-sectional descriptive study of 23 adult patients diagnosed with PAN between January 2011 and December 2018 in two high complexity hospitals in Medellin-Colombia. Results: twenty-three patients met ACR 1990 classification criteria for PAN, 52% were men with a median age of 51 (IR 36-60), 78.3% were newly diagnosed, and only two patients (8.7%) had HBV infection. General symptoms (found in 95% of the patients), cutaneous (82%), and articular (56%) were the most frequent manifestations. Among systemic symptoms, myalgia, especially calf pain, was the most common characteristic (78.3%), followed by weight loss (73.9%), fatigue (69.3%), and fever (59.3%). Laboratory findings and severity scores are shown in the table. Angiography was performed in 27.3% of patients, finding splanchnic (renal, hepatic and splenic) microaneurysms (17.4%), stenosis (13%), and renal infarction (4.3%). Fourteen patients (61%) had at least one positive biopsy documenting medium-sized artery vasculitis, mainly skin, muscle, nerve, or both; 9 (39%) had normal or inconclusive biopsy findings. All patients received high daily doses of prednisolone (50 ± 16 mg); 52.2% required cyclophosphamide, 30.4% azathioprine, 17.4% methotrexate, 8.7% rituximab, 4.3% dapsone and 4.3% plasmapheresis; acetylsalicylic acid was given to half of the patients and only one required antiviral therapy for HBV. With treatment, 87% improved; 22.7% had an infection, and 8.7% of patients died. Conclusion: myalgia was the main characteristics of our PAN patients, especially in calves, and its presence in patients with other general, skin or articular symptoms should raise the suspect of this vasculitis. References: [1]Karadag O, Jayne DJ. Polyarteritis nodosa revisited: a review of historical approaches, subphenotypes and a research agenda. Clin Exp Rheumatol. 2018;36 Suppl 111(2):135–142. [2]Pagnoux C, Seror R, Henegar C, et al. Clinical features and outcomes in 348 patients with polyarteritis nodosa: a systematic retrospective study of patients diagnosed between 1963 and 2005 and entered into the French Vasculitis Study Group Database. Arthritis Rheum. 2010;62(2):616–626. Disclosure of Interests: None declared