Chronic polyarthritis as the first manifestation of childhood systemic polyarteritis nodosa

ABSTRACT Arthritis has been reported as an acute pattern, generally evanescent with oligoarthritis, mostly affecting knees and ankles in childhood systemic polyarteritis nodosa. However, chronic polyarthritis with morning stiffness mimicking juvenile idiopathic arthritis has not been reported. We describe the case of a 4-year old girl who had additive and chronic polyarthritis with edema, tenderness, pain on motion and morning stiffness for 2 months. After 45 days, she also presented painful subcutaneous nodules and erythematous-violaceous lesions in the extensor region of upper and lower limbs. She was admitted to university hospital due to high fever, malaise, myalgia, anorexia, loss of weight (1kg), painful skin lesions and severe functional disability. She was bedridden by chronic polyarthritis with limitation on motion. Systolic and diastolic blood pressures were greater than 95th percentile for height. Urine protein/creatinine ratio was 0.39g/day, and immunological tests were negative. Anti-streptolysin O was 1,687UI/mL. Skin biopsy revealed necrotizing vasculitis in medium- and small-sized vessels compatible with polyarteritis nodosa. Therefore, we had the diagnosis of systemic polyarteritis nodosa. Prednisone 2mg/kg/day was administered with complete resolution of skin lesions and arthritis, and improvement of proteinuria (0.26g/day) after 15 days. The diagnosis of childhood systemic polyarteritis nodosa should be considered for patients with chronic polyarthritis associated to cutaneous vasculitis triggered by streptococcal infection.