Eosinophilic Granulomatosis With Polyangiitis (EGPA) Hidden in Acute Appendicitis: A Case Revealed Through Histopathological Examination

Abstract

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare form of necrotising vasculitis characterised by eosinophilic infiltration and systemic involvement, most commonly affecting the lungs, skin, and peripheral nerves. Gastrointestinal (GI) manifestations are common in patients with EGPA, although histopathological confirmation of GI involvement is infrequent. Acute appendicitis is a common surgical emergency, but its presentation as an initial manifestation of EGPA is exceptionally uncommon. We report the case of a 54-year-old man with a history of asthma who presented with fever and epigastric pain that later migrated to the right lower quadrant. Laboratory tests revealed leukocytosis and elevated C-reactive protein levels. Abdominal computed tomography (CT) demonstrated mild appendiceal enlargement, and a diagnosis of acute appendicitis was made. The patient underwent laparoscopic appendectomy. Postoperatively, he developed persistent lower abdominal pain, new-onset bilateral lower extremity pain, and marked eosinophilia (60%). Histopathological examination of the resected appendix revealed dense eosinophilic infiltration and necrotising vasculitis, establishing the diagnosis of ANCA-negative EGPA. This phenotype is known to present with gastrointestinal manifestations and peripheral eosinophilia frequently. He was subsequently transferred to a specialised centre for further treatment. This case highlights the potential for EGPA to mimic acute appendicitis. When persistent eosinophilia and atypical postoperative symptoms are present, systemic diseases such as EGPA should be considered. Histopathological analysis plays a pivotal role in identifying underlying systemic vasculitis, particularly in cases with unusual clinical presentations. Greater awareness of EGPA as a differential diagnosis in atypical appendicitis may facilitate earlier recognition and timely management.

Keywords: acute appendicitis; egpa; eosinophilia; histopathological examination; surgical emergency.

Figure 1. Abdominal computed tomography showing mild enlargement of the appendix.

(a) Axial view (b) Coronal view.

Figure 2. Intraoperative findings.

(a) The appendix was adherent to the cecum and mildly enlarged (b) Ascitic fluid was observed in the pelvic cavity.

Figure 3. Postoperative changes in inflammatory markers.

(a) White blood cell and eosinophil counts (b) C-reactive protein levels.

Figure 4. Histopathological findings for the appendix.

(a) In the appendiceal specimen, the mucosa appeared atrophic on gross examination (b) Blood vessel walls stained red with Elastica Van Gieson staining (c) Hematoxylin and eosin staining of the appendiceal artery revealed fibrinoid necrosis of the vascular walls. Dense infiltration of inflammatory cells and histiocytes was observed, leading to luminal obstruction (d) An enlarged view  showing perivascular infiltration of eosinophils and neutrophils.

Figure 5. Immunofluorescence staining.

(a) IgG staining (X400): Negative, (b) IgA staining (X400): Negative, (c) IgM staining (X400): Negative, (d) C3c staining (X400): Negative, (e) Fibrinogen staining (X400): Negative. All images demonstrate the absence of immune complex deposition. All of the staining tests were negative.