A rare case of granulomatosis with polyangiitis (GPA) affecting a thin layer of the abdomen — with no detectable anti-neutrophil cytoplasmic antibodies (ANCA) — was reported by researchers at Mitsui Memorial Hospital in Tokyo, Japan.
The case report “Granulomatosis with Polyangiitis Localized in the Greater Omentum” was published in the journal Case Reports in Surgery.
GPA, a subtype of ANCA-associated vasculitis, is an autoimmune disorder characterized by progressive deterioration of small- and medium-sized blood vessels. While the disease usually affects the lungs and kidneys, if can cause inflammation in several other organs.
Increased levels of ANCA autoantibodies are considered a hallmark of this disease. But in some patients, blood tests come up negative for ANCA antibodies.
Researchers presented the case of a 91-year-old man who developed GPA in the greater omentum, and presented no signs of ANCA antibodies in circulation, which made his diagnosis harder. The greater omentum is a thin layer in the abdominal cavity.
The patient arrived at the emergency room complaining of abdominal pain and fever. A physical examination confirmed the patient had increased sensitivity in the abdominal region, with no signs of tissue damage or other obvious abnormal findings affecting the ears, nose, or skin.
Blood analysis revealed increased inflammation with elevated white blood cell counts and C-reactive protein. The patient also had increased levels of creatinine in the blood, which suggested acute kidney injury, but urine analysis was normal. Chest radiography and computed tomography (CT) scan found no tumor lesions or abnormalities.
Additional blood testing showed the patient was negative for ANCA antibodies. While physicians did not detect any pathogen that could be causing an infection, they decided to start treatment with the antibiotic Zosyn (tazobactam/piperacillin).
Later, the patient developed a new sign of irritation in the abdominal region. New CT scans showed fluid accumulation in the lower abdomen and increased inflammation of the greater omentum and ileocolic mesentery (fat tissues that surround the intestines and maintain their integrity).
Blood test confirmed that inflammation was still high, but renal function had returned to normal. The patient was given another kind of antibiotic — Merrem (meropenem) — but fever, abdominal pain, and inflammation did not disappear.
As physicians could not define the cause for all the symptoms, they performed a small invasive surgical evaluation (laparotomy), where they found inflammation of the greater omentum. Tissue analysis confirmed blood vessel inflammation, which was consistent with a GPA diagnosis.
The patient was treated with methylprednisolone for three days, followed by daily prednisolone. One year later, he had no symptoms or signs of inflammation.
“This report reminds physicians to consider GPA in the differential diagnosis of acute abdominal pain or fever of unknown origin,” the researchers wrote.
“An early diagnosis could contribute to not only treatment but also the prevention of severe abdominal manifestations, such as perforation or intra-abdominal bleeding,” they added.