A 91-year-old man presented with abdominal pain and was followed up to 2 days. On physical examination, periumbilical tenderness was found, but there were no peritoneal irritation signs or other obvious abnormal findings of the ears, nose, or skin. The blood test results showed a high inflammatory reaction (white blood cell (WBC) count 13,800/microL; C-reactive protein (CRP) level 33.5 mg/L) and acute kidney injury (creatinine (Cre) 1.11 mg/dL). Urinalysis was normal. The chest radiography demonstrated no remarkable change. The computed tomography (CT) scan was negative for any infectious focus or other abnormal findings, such as cavitating nodules in the lungs or other site neoplasms. Antibiotics (tazobactam/piperacillin 13.5 g/day) were administered as empiric therapy.
After hospitalisation, the patient developed fever over 39 C. Results of the blood cultures and other cultivation tests were all negative, including the tuberculosis test. Additional analyses demonstrated a negative ANCA titer, proteinase 3- (PR3-) ANCA, and myeloperoxidase- (MPO-) ANCA. Two days later, the patient showed a new peritoneal irritation sign at the periumbilical and right lower abdomen. The CT scan showed an increased CT value of the greater omentum and ileocolic mesentery, and ascites (Figure 1). Blood test results showed that the inflammatory reaction was still high (WBC count 20,700/microL; CRP level 29.3 mg/L), although renal function returned to normal (Cre level 0.93 mg/dL). The antibiotics were changed (meropenem 3 g/day), but the fever and abdominal pain did not disappear, and inflammatory reaction remained at a high level.
Because there was no sign of infectious focus for fever and abdominal pain, except for an increased CT value of the omentum and ascites, examination laparotomy was planned. Laparotomy revealed diffuse redness and swelling of the greater omentum and pale haemorrhagic ascites (Figure 2). Histological examination of the resected omentum demonstrated both arteritis and more severe venulitis, focal necrotizing vasculitis of the venules, and palisading granuloma (Figures 3(a) and 3(c)).
The patient was diagnosed as having GPA based on the Chapel Hill Consensus Conference 2012 definitions and treated with intravenous methylprednisolone pulse therapy (1000 mg/day for 3 days). Subsequently, daily prednisolone was administered, and the dose was gradually tapered to 15 mg over 1 month. The patient was discharged without relapse.
One year later, the patient did not show any symptoms, and the follow-up CT scan showed no sign of vascular inflammation.