Fever, weight loss, and leg myalgia in a 59-year-old man

In March, 2020, a 59-year-old man presented to Hospital Universitario 12 de Octubre, Madrid, Spain, with a 15-day history of fever, headache, leg myalgia, and weight loss (4 kg). Physical examination showed no pathological findings. Initial diagnostic workup showed an increased concentration of C-reactive protein (16 mg/dL) and lymphopenia (700 lymphocytes per μL). White blood cell count and concentrations of creatine kinase were normal (52 units per L; reference range: 34–171 units per L). Nasopharyngeal exudate was negative for influenza A and B, respiratory syncytial virus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A chest radiograph showed no abnormalities. Symptomatic treatment with oral analgesics and antipyretics (paracetamol 650 mg every 8 h, alternating every 4 h with dipyrone 575 mg every 8 h) was initiated, and the patient showed clinical improvement 4 days after admission. The patient was discharged and scheduled for a follow-up 3 weeks later. At 7 days after discharge, the fever and headache recurred. The patient did not seek medical attention and was not evaluated by a physician until the 3-week follow-up. During this follow-up, the patient reported the fever and headache recurrence, and analysis indicated increased concentrations of inflammatory markers (14 mg/dL of C-reactive protein and an erythrocyte sedimentation rate of 46 mm per h). The patient was readmitted to the hospital and a PET scan was done, which showed an increase in metabolic activity on the vascular walls of small and medium vessels. A subsequent visceral arteriography showed multiple microaneurysms in the small arteries of the digestive visceral territory and both renal arteries, which suggested polyarteritis nodosa vasculitis (figure ). Tests for antinuclear antibodies and antineutrophil cytoplasmic antibodies were negative. Hepatitis B virus, hepatitis C virus, and HIV serological tests were negative. There was no evidence to suggest the involvement of other organs (five factor score=0). The patient received treatment with intravenous methylprednisolone bolus for 2 days (120 mg daily). The patient was discharged and received oral azathioprine (100 mg daily for 1 week, followed by 150 mg daily indefinitely) and a tapering regimen of oral prednisone (30 mg daily for 1 week, followed by 20 mg daily for 1 week, 1 week off, 10 mg daily for 2 weeks, alternate daily doses of 10 mg and 7·5 mg for 2 weeks, and 7·5 mg daily indefinitely). At the 3-week follow-up, fever, headache, and myalgia had resolved.

Figure.

Scattered microaneurysms involving small vessels

Imaging of small vessels in the inferior mesenteric artery (A), superior mesenteric artery (B), and left renal artery (C). The arrows indicate microaneurysms.

Polyarteritis nodosa is a rare necrotising vasculitis of medium and small arteries, with substantial associated morbidity and mortality. Clinical features are highly variable; symptoms at onset are usually unspecific, and the differential diagnosis is often broad. Because the patient was admitted during the COVID-19 pandemic, the possibility of an infection with SARS-CoV-2 was initially considered; however, the poor clinical and analytical improvement prompted us to look for other causes of the symptoms and laboratory abnormalities. Accurate diagnosis of polyarteritis nodosa allowed for early initiation of immunosuppressive treatment.