Microscopic polyangiitis (MPA) is a rare autoimmune disease characterized by the inflammation and necrosis of small vessels, primarily affecting kidneys and lungs. It is classified as an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) due to the presence of ANCA. MPA can manifest as diffuse alveolar hemorrhage (DAH) and rapidly progressive glomerulonephritis. In contrast, rheumatoid arthritis (RA) is an inflammatory disease that mainly targets the synovial joints. The coexistence of these two conditions presents significant diagnostic challenges, highlighting the need for further research and understanding. We report a case of a 58-year-old male with a past medical history of RA, chronic bronchitis, tobacco use, and recent Legionella pneumonia who presented with acute dyspnea. The patient was intubated for acute hypoxemic respiratory failure. Laboratory workup revealed anemia, hyponatremia, and acute kidney injury. Urinalysis showed hematuria and proteinuria. A CT scan of the chest exhibited bilateral extensive patchy infiltrates. He was transfused with one packed red blood cell (PRBC) unit. Hemoglobin decreased below 6 g/dL after transfusion. A bronchoscopy revealed erythema throughout the tracheobronchial tree, and blood on bronchial alveolar lavage suggested DAH. High-dose steroids were started. Subsequent laboratory results were positive for rheumatoid factor (RF), perinuclear ANCA (p-ANCA), anti-myeloperoxidase (anti-MPO), and antinuclear antibody (ANA). The kidney biopsy demonstrated focal crescentic necrotizing glomerulonephritis pauci-immune type, confirming MPA. RA pathogenesis involves immune dysregulation and activation of various cells, leading to the release of cytokines. Antibodies such as RF and anti-cyclic citrullinated peptide (anti-CCP) can be detected up to 10 years before the clinical manifestation of RA. Recent studies have revealed a predominance of MPA in AAV while coexisting with RA. The underlying mechanism of its occurrence remains unclear. Our patient had recurrent respiratory symptoms and renal dysfunction before hospitalization. MPA-RA overlap syndrome is potentially treatable and clinicians should maintain a high index of suspicion when encountering patients with preexisting RA. Timely initiation of immunosuppressive therapy at early stages is essential to prevent renal and pulmonary complications. ANCA serology should be assessed in these cases.

Hydralazine-induced anti-neutrophil cytoplasmic antibody (ANCA) vasculitis may occur any time after hydralazine initiation. General internists should recognize diffuse alveolar hemorrhage (DAH) as a rare complication of this condition, as early treatment reduces the associated high risk of mortality. We describe the case of an 82-year-old female with diastolic heart failure who presented with a one-month history of worsening dyspnea on exertion and a one-week history of scant hemoptysis and fatigue. Her medications included aspirin and hydralazine. She was hypoxic with bilateral expiratory wheezes on exam. Labs showed new anemia, elevated creatinine, proteinuria, and hematuria. Chest computed tomography showed asymmetric bilateral upper lobe ground-glass attenuation superimposed on interlobular septal thickening and intralobular lines. Further testing showed anti-nuclear antibody, positive ANCA, perinuclear ANCA (p-ANCA), and anti-myeloperoxidase ANCA (anti-MPO-ANCA). Renal biopsy revealed MPO-ANCA, pauci-immune, necrotizing, and crescentic glomerulonephritis. She was diagnosed with DAH secondary to hydralazine-induced ANCA-associated vasculitis (AAV). Hydralazine is an anti-hypertensive medication with known potential for autoimmune reactions. Of these, AAV is a rare sequela mediated by anti-MPO and most commonly affects the kidneys. In rare circumstances, patients with AAV can develop pulmonary-renal syndrome, resulting in both glomerulonephritis and DAH with an associated high risk of mortality. Diagnosis requires a high index of suspicion in patients with acute kidney injury of unclear etiology. Early diagnosis through immune work-up and kidney biopsy should be pursued, as prompt recognition of the vasculitis, cessation of hydralazine, immunosuppression, and early plasma exchange are essential to an improved prognosis.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease and there is a distinct differentiation of clinical manifestations. Lupus nephritis (LN) is clinically apparent in approximately half of patients. A kidney biopsy is essential to define the kidney injury, exclude other injurious causes, and determine the histopathologic subtypes. Autoantibodies are crucial to the pathogenesis and the deposition of immune complexes in glomeruli is a hallmark of LN. The histopathology of LN is quite varied. Despite pauci-immune LN being an unexpected condition in SLE, it has been observed rarely with the presence of antineutrophil cytoplasmic autoantibodies (ANCA). We present a young male who was admitted to the emergency with syncope. The brain imaging revealed small infarct areas and signs of cerebral vasculitis. Also, he had elevated inflammatory markers, moderate proteinuria, and preserved kidney function. Anti-nuclear antibodies and anti-dsDNA were positive. Pauci-immune crescentic glomerulonephritis (PICGN) was observed in a kidney biopsy, however, ANCA was negative. SLE diagnosis was established by neurological manifestation, specific antibodies, proteinuria, and kidney biopsy findings. We administered a combination induction regimen, including pulse steroid and parenteral cyclophosphamide. The proteinuria was resolved in the follow-up. Our case highlights that SLE-associated ANCA-negative PICGN can be the initial presentation in the absence of typical manifestations. LN exhibits various pathological mechanisms in the kidney. As a consequence, SLE should be considered in the differential diagnosis of all forms of kidney injury.

Granulomatosis with polyangiitis (GPA) is a relatively rare systemic autoimmune disorder of small and medium size blood vessels affecting multiple organs with a wide range of clinical presentations. We present a 57-year-old Caucasian male who presented to the ER with midsternal chest pain. He was hospitalized for non-ST elevated myocardial infarction (NSTEMI) and later diagnosed with pauci-immune necrotizing crescentic glomerulonephritis confirmed with renal biopsy.

Vasculitis, or inflammation of blood vessels, is commonly seen with severe acute respiratory syndrome Coronavirus disease 2 (SARS-CoV-2). It is usually triggered by an autoimmune response induced by the virus, infection by the virus itself and trauma to the epithelial vessels caused by the release of cytokines. We present a case of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (pauci-immune crescentic glomerulonephritis [GN]) superimposed on acute kidney injury caused by SARS-CoV-2. Our patient is a 57-year-old Hispanic female who presented with rising creatinine and active urinary sediment in the setting of an asymptomatic COVID-19 infection. A kidney biopsy was done for declining renal function, and positive myeloperoxidase antibodies revealed pauci-immune focal crescentic glomerulonephritis. Normalization of renal function was not achieved with pulse steroids and rituximab. The patient required long-term hemodialysis. Our case here adds to the very few cases of pauci-immune crescentic glomerulonephritis reported in patients with asymptomatic SARS-CoV-2 infection. We recommend keeping this high on the differential in SARS-CoV-2-infected patients presenting with acute kidney injury.

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BACKGROUND: Diffuse crescentic IgAN (CIgAN) is an uncommon phenotype of IgAN, which presents as rapidly progressive renal failure, similar to patients with pauci-immune crescentic glomerulonephritis(PCGN). There are limited data on outcomes comparisons between the two.
METHODS: In this single-center, retrospective cohort study, we compared the clinical features, pathological presentation, and renal outcomes of 52 patients with CIgAN and 42 patients with renal-limited PCGN from January 2007 to December 2019.
RESULTS: The CIgAN patients were younger (30.5 ± 13.8 years) than PCGN patients (46.1 ± 11.8 years) (P = 0.001). The CIgAN patients had a higher prevalence of hypertension (86.5% Vs. 41.3%, P = 0.001); and degree of proteinuria (4.2 ± 2.7 g/24 h Vs. 2.3 ± 1.16 g/24 h; P = 0.001) than PCGN patients. The chronicity in terms of global glomerulosclerosis, interstitial fibrosis, and tubular atrophy was higher in the CIgAN group than in the PCGN group. The remission rate with immunosuppression was significantly higher in the PCGN group than in the CIgAN group (P = 0.016). The end-stage renal disease (ESRD) or death within 1 year of diagnosis was significantly more in the CIgAN group (62.3% Vs. 39.1%) than PCGNgroup. For patients who were dialysis-dependent at presentation, the primary outcome of ESRD or death within one year was seen in 90.9% of patients of CIgAN and 44.1% in the PCGN group (P = 0.001). The long-term death non-censored renal survival is poor in the CIgAN group than in PCGN patients. However, patient survival is poor in PCGN patients.
CONCLUSIONS: CIgAN is a different form of RPGN compared to PCGN and carries a poor prognosis despite similar immunosuppressive therapy in the long term.

Hydralazine is a vasodilator used in the treatment of resistant hypertension. It is a safe and widely used antihypertensive medicine. Its common adverse effects include headache, rebound tachycardia, fluid retention, and angina. It is a rare cause of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) with pulmonary and renal involvement. We report a case of a 74-year-old woman, with over eight years of use of hydralazine, who presented to the hospital with shortness of breath and cough. Blood work revealed deranged renal function with high creatinine levels. Serology workup was positive for anti-histone antibodies (AHA), anti-nuclear antibodies (ANA), myeloperoxidase (MPO) ANCA and proteinase-3 (PR-3) ANCA. Renal biopsy showed diffusely flattened tubular epithelium, focal micro vesicular degeneration, and focal loss of the brush border of the proximal tubular epithelium. Hydralazine was stopped and the patient was treated with corticosteroids, resulting in the resolution of her kidney injury.

Renal involvement in systemic lupus erythematosus is usually exhibited as lupus nephritis, which is a form of immune complex-mediated glomerulonephritis and one of the most severe organ manifestations of systemic lupus erythematosus. The pathogenesis involved glomerular immune complex deposition, which leads to glomerular inflammation and typically shows a \"full-house\" pattern on immunofluorescence microscopy. Other forms of glomerulonephritis are rarely observed in patients with systemic lupus erythematosus. Pauci-immune crescentic glomerulonephritis is the pattern of injury most commonly observed in patients with antineutrophil cytoplasmic autoantibody-associated glomerulonephritis. The characteristic histological feature of pauci-immune crescentic glomerulonephritis is focal necrotizing and crescentic glomerulonephritis with little or no glomerular staining for immunoglobulin by immunofluorescence microscopy. We report a rare case of antineutrophil cytoplasmic autoantibody-negative pauci-immune crescentic glomerulonephritis in a patient with systemic lupus erythematosus.

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