Granulomatosis With Polyangiitis: The Complexity of Clinical Manifestations, Therapeutic Challenges, and Complications of a Severe Multisystemic Case

We report a case of a 34-year-old male with severe multisystemic involvement (including the testis, musculoskeletal system, skin, upper respiratory tract, ocular system, peripheral nerves, abdomen, and kidney) due to granulomatosis with polyangiitis (GPA) and a high proteinase 3 (PR3)-antineutrophil cytoplasmic antibodies (PR3ANCA) titer. A renal biopsy showed pauci-immune glomerulonephritis (GN). Systemic corticotherapy combined with cyclophosphamide was chosen for induction therapy. During the induction phase, clinical deterioration occurred in the form of severe alveolar hemorrhage, leading to admission to the intensive care unit (ICU). Influenza A (H1N1) was detected in the respiratory tract. Furthermore, blood sampling revealed an invasive Klebsiella pneumoniae infection that persisted despite multiple antibiotic regimens. A CT scan showed splenic vascular compromise, assumed to be the primary source of the infection, with sustained improvement after splenectomy. Maintenance therapy included a tapering dose of corticotherapy for 36 months and azathioprine 100mg daily for five years, which achieved full and sustained remission. The patient has been in full remission for nine years, with mild renal sequelae, including proteinuria and secondary hypertension.