Autori: Stefano Bani
Affiliazioni: Azienda Ospedaliero-Universitaria di Parma
INTRODUCTION: ANCA-associated vasculitis (AAV) is a rare form of systemic vasculitis that predominantly involves body’s small-medium vessels. AAV are characterized by the absence or a paucity of immunoglobulin deposition in vessel walls. AAV has different clinicopathologic phenotypes, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic GPA (EGPA), and renal-limited necrotizing and crescentic glomerulonephritis (NCGN). The two major target antigens for ANCA in patients with vasculitis are myeloperoxidase (MPO) and proteinase 3 (PR3) in the granules of neutrophils and lysosomes of monocytes. The specificity of ANCA for MPO versus PR3 correlates with the spectrum of pathologic and clinical features of respectively MPA or GPA.
CASE REPORT: 77 years old white caucasian woman whit several week history of flu-like symptoms, worsening dyspnea and haemoptysis referring to emergency department with Diffuse Alveolar Hemorrhage (DAH) and Acute kidney Injury (AKI). His medical history was remarkable for hypertenson. Chest X-ray showed diffuse parenchymal thickening with ground-glass aspect. The following high resolution CT scan confirmed diffuse parenchymal thickening involving all pulmonary lobes with ground glass aspects highly suggestive of DAH. Blood test revealed a marked alteration of renal function (s-Creat. 4.4 mg/dl vs 0.6 mg/dl baseline; BUN 93.8 mg/dl) and severe anemia (Hb 6.3 mg/dl). Patient had normal urinary output.
Were then performed 1) abdomen ultrasonography (u.s.) revealing small kidney, with hyperechoic parenchyma like chronic kidney disease (CKD). 2) urinalisys showing proteinuria (>30 mg/dl) associated with micro-hematuria 3) immunologic blood test with evidence of 1/10 positive MPO p-ANCA title and 1/80 positive ANA title (nuclear laminis pattern). Over the next few days, the patient deteriorated developing respiratory failure requiring noninvasive ventilation support (BiPAP). Reasonably suspecting AAV steroid therapy i.v. was started in association with plasma exchange (five session) obtaining a slowly but steady improvement of renal function(s-creat. 3.7 mg/dl) and improvement of gas alveolar exchange, with improvement of x-ray imaging, leading to hospital discharge. Renal biopsy wasn’t performed.
DISCUSSION: on the bases of 1) clinical findings, 2) imaging test result 3) p-ANCA MPO positive blood test and 4) response to steroids plus plasma exchange therapy we suspected AAV more specifically MPA due to MPO positive assay. MPA is a necrotizing systemic vasculitis of small to medium sized vessels that can result in a wide spectrum of organ involvement, but predominantly affects the kidneys (80- 100%) more so than the lungs (22-55%). Patients generally present beyond their 4th decade of life, and onset of symptoms is most often insidious in nature, with the rare patient presenting acutely, particularly with acute respiratory failure. Diffuse alveolar hemorrhage due to alveolar capillariitis is the most frequent lung manifestation of MPA for all ages. However, with few exceptions, acute respiratory failure is almost never the initial manifestation of MPA. (A study aiming to describe the pulmonary manifestations of MPA illustrated 29 cases of DAH. Of these cases, 69% had severe dyspnea but only 10% required treatment with mechanical ventilation). In our case the disease started, not so commonly according to literature findings, with severe respiratory failure and needing of non-invasive ventilation support. Lower respiratory tract involvement was accompanied by AKI. Medical history negative for CKD appear in contrast with the u.s. finding of small kidney, very CKD likely; however not having performed renal biopsy the etiology of kidney involvement remain unclear, being attributable to both nephrangiosclerosis or AAV with slowly progressive renal involvement
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