Clinical and pathological features of anti-neutrophil cytoplasmic antibody-associated vasculitis in patients with minor urinary abnormalities

A case of renal limited myeloperoxidase anti-neutrophil cytoplasmic antibody-positive vasculitis treated with maintenance avacopan monotherapy

A 76-year-old woman was admitted with progressive renal function decline. A kidney biopsy was performed because of myeloperoxidase anti-neutrophil cytoplasmic antibody (ANCA; 333 IU/mL), proteinuria (1.21 g/d), and urinary erythrocyte sediment (10-19/high-power field). Renal-limited ANCA-positive vasculitis with pauci-immune necrotizing crescentic glomerulonephritis (ANCA-associated vasculitis, AAV) was diagnosed. Glucocorticoid therapy was started, and the patient responded well. About 1 year later, avacopan treatment was started and glucocorticoid therapy was discontinued. Avacopan did not normalize ANCA levels and did not make urinary findings negative. However, further progression of renal function decline is prevented. Factors attributed to the development of AAV in this case were investigated; AAV developed after the second dose of the COVID-19 vaccine and ANCA levels re-elevated after the fifth dose. This suggests that the COVID-19 vaccine may have contributed to the development of AAV in this elderly patient. Avacopan monotherapy has been shown to be effective as maintenance therapy to control the progression of renal failure although not sufficient for complete remission of AAV.

[Management of ANCA-associated vasculitides]

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune-mediated inflammation of small and medium-sized vessels that can affect virtually any organ system and bears the risk of irreversible organ damage. Without treatment the mortality rates are high, which necessitates rapid diagnosis and initiation of treatment. Histological confirmation, which is not feasible in all cases, should be strived for, especially to delineate differential diagnoses and vasculitis mimics. The new American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) classification criteria are primarily designed for study purposes and show limitations in the routine application. Globally, the recently updated EULAR recommendations represent the most up to date management guidelines. Therapeutically, rituximab and cyclophosphamide in combination with glucocorticoids remain the pillars of treatment in remission induction for severe organ-threatening and life-threatening diseases. For the first time, mepolizumab and avacopan represent approved treatment options for specific entities that make a significant contribution to steroid reduction. New attention has been paid to patient-reported outcomes, for which a disease-specific outcome questionnaire is now available.

Kidney biopsy in patients with antineutrophil cytoplasmic antibody-associated vasculitis with mild renal abnormality

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a systemic inflammation of small or medium blood vessels that includes microscopic polyangiitis. A diagnosis of ANCA-associated vasculitis can be aided by histological identification of vasculitis, and identification of renal impairment can help predict outcomes. However, kidney biopsy is not generally indicated in the absence of renal findings. We report two cases of ANCA-associated vasculitis diagnosed by kidney biopsy despite the absence of remarkable urinary abnormality and renal impairment. These patients had fever of unknown origin and were positive for myeloperoxidase (MPO)-ANCA but showed few findings that would suggest small-vessel vasculitis in the kidney. Nevertheless, kidney biopsies revealed small-vessel arteritis, necrotizing glomerulonephritis, and interstitial nephritis. Immunofluorescent antibody tests performed using samples of glomeruli were all negative, suggesting microscopic polyangiitis. Therefore, kidney biopsy may be useful in confirming the diagnosis, even if patients have completely normal urinary findings in the absence of other organ lesions.

Cholesterol Emboli Co-Existing with Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis in a 76-Year-Old Woman

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis injures small vessels and causes severe systemic organ injury. Main target antigens of ANCA are myeloperoxidase and proteinase 3. ANCA strongly associates with the development and progression of the vasculitis. Its manifestations include rapidly progressive glomerulonephritis, interstitial pneumonitis, alveolar hemorrhage, purpura, and neurological disorder. Most patients with ANCA-associated vasculitis in Japan are elderly and have atherosclerotic risk factors. Cholesterol emboli are systemic vascular inflammation triggered by cholesterol crystals. Cholesterol emboli cause kidney dysfunction and ischemia of the intestines, brain, heart, skin, and peripheral nerves. Diabetes mellitus, hypertension, hyperlipidemia, and history of cardiovascular diseases are risk factors of the development of cholesterol emboli. We report a case of ANCA-associated vasculitis coexisting with cholesterol emboli. A 76-year-old woman was diagnosed with ANCA-associated interstitial pneumonitis. She rapidly developed progressive glomerulonephritis, purpura, and peripheral sensory nerve disorder. A kidney biopsy revealed that renal dysfunction was caused by vasculitis of the interlobular arteries and cholesterol emboli. A skin biopsy revealed that purpura was caused by cholesterol emboli. Glucocorticoid and statin therapies were administered. Thereafter, the renal function and other symptoms improved and stabilized. The representative symptoms of ANCA-associated vasculitis and cholesterol emboli are closely similar, and it is difficult to distinguish between these diseases when they coexist. Because the background characteristics of patients with ANCA-associated vasculitis and risk factors of cholesterol emboli overlap, at the time of diagnosing ANCA-associated vasculitis, clinicians should consider the possibility of cholesterol emboli coexistence.

ANCA-associated nephritis without crescent formation has atypical clinicopathological features: a multicenter retrospective study

BACKGROUND

Although crescentic glomerulonephritis is a hallmark of ANCA-associated nephritis, the clinicopathological features of ANCA-associated nephritis without crescent formation remain to be elucidated.

METHODS

We enrolled 146 Japanese ANCA-associated vasculitis (AAV) patients subjected to renal biopsy in 16 hospitals from 2001 to 2018, and compared those with and without crescent formation (C + and C- groups). The primary endpoint was end-stage renal disease (ESRD) and/or death.

RESULTS

C- group comprised 25 (17.1%) subjects. They had better renal function at the time of renal biopsy [estimated glomerular filtration rate (eGFR); median 41.7 vs 27.5 ml/min/1.73 m², p < 0.01] with minor urinary abnormalities but had a higher serum C-reactive protein level (8.8 vs 5.4 mg/dl, p = 0.01) and frequency of extra-renal lesions of AAV (76.0% vs 48.8%, p = 0.02) than C + group. Pathologically, C- group had a higher frequency of arteritis (40.0% vs 16.5%, p < 0.01). Kaplan-Meier method with log-rank tests showed no significant difference in renal and life prognosis combined, regardless of crescent formation. Multivariate Cox regression analysis revealed baseline eGFR, sclerotic class, and extra-renal lesions to be risk factors of ESRD and death combined. Competing risk analysis showed baseline eGFR and sclerotic class to be associated with ESRD, whereas baseline eGFR and extra-renal lesions were associated with death.

CONCLUSION

ANCA-associated nephritis without crescent formation had different clinicopathological features from those with crescent formation, suggesting an atypical subtype of ANCA-associated nephritis. Despite the better renal function at the time of renal biopsy, these results suggest that this subtype requires especially careful attention, especially in the presence of extra-renal involvement.