Significance of clinical-immunological patterns and diagnostic yield of biopsies in microscopic polyangiitis and granulomatosis with polyangiitis.

BACKGROUND: Microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) are the two major antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). OBJECTIVES: To characterize a homogenous AAV cohort and to assess the impact of clinicopathological profiles and ANCA serotypes on clinical presentation and prognosis. Clinical differences in GPA patients according to ANCA serotype and the diagnostic yield for vasculitis of biopsies in different territories were also investigated. RESULTS: This retrospective study (2000-2021) included 152 patients with AAV (77 MPA/75 GPA). MPA patients (96.1% myeloperoxidase [MPO]-ANCA and 2.6% proteinase 3 [PR3]-ANCA) presented more often with weight loss, myalgia, renal involvement, interstitial lung disease (ILD), cutaneous purpura, and peripheral nerve involvement. Patients with GPA (44% PR3-ANCA, 33.3% MPO, and 22.7% negative/atypical ANCA) presented more commonly with ear, nose, and throat and eye/orbital manifestations, more relapses, and higher survival than patients with MPA. GPA was the only independent risk factor for relapse. Poor survival predictors were older age at diagnosis and peripheral nerve involvement. ANCA serotypes differentiated clinical features in a lesser degree than clinical phenotypes. A mean of 1.5 biopsies were performed in 93.4% of patients in different territories. Overall, vasculitis was identified in 80.3% (97.3% in MPA and 61.8% in GPA) of patients. CONCLUSIONS: The identification of GPA presentations associated with MPO-ANCA and awareness of risk factors for relapse and mortality are important to guide proper therapeutic strategies in AAV patients. Biopsies of different affected territories should be pursued in difficult-to-diagnose patients based on their significant diagnostic yield.

Simultaneous presentation of granulomatosis with polyangiitis (GPA) and immunoglobulin G4-related disease (IgG4-RD). Leaving an open question: widening the spectrum of a single disease or real overlap?

Because of a similar organ involvement and histopathological features, IgG4-related disease (IgG4-RD) may mimic some forms of granulomatosis with polyangiitis (GPA). However, several cases of clear coexistence or overlap of both diseases have been reported. We describe a case of a 47-year-old man presenting with a renal mass and a nasal crusting showing histopathological features of IgG4-RD in both territories. Cytoplasmic/proteinase 3 (PR3) antineutrophil cytoplasmic antibodies (ANCA) were positive and the patient subsequently developed kidney failure and nephritic syndrome that led to a renal biopsy re-evaluation revealing changes compatible with segmental necrotising glomerulonephritis and GPA. Remission induction therapy with prednisone and rituximab was started and clinical and laboratory parameters returned to normal. After administering a maintenance regimen based in rituximab 500 mg every six month the patient remained asymptomatic during 4 years of follow-up and free of prednisone the last 18 months. Although coexistence or overlap of GPA and IgG4-RD may be established in some clinical scenarios, the possibility of widening the spectrum of a single disease is also postulated.