An unusual form of kidney injury without glomerulonephritis in microscopic polyangiitis: a case report.

BACKGROUND: Microscopic polyangiitis (MPA), a kind of antineutrophil cytoplasmic autoantibody associated vasculitis (AAV), predominantly affects small-sized vessels. MPA is a significant cause of the pulmonary-renal syndrome. Pauci-immune necrotizing and crescentic glomerulonephritis is the typical renal histological feature of AAV. Tubulointerstitial lesions may occur and mostly form with inflammatory cell infiltration in the interstitium. However, a few cases reported only tubulointerstitial involvement without glomerular lesions in patients with MPA. CASE PRESENTATION: We present an MPA case, a 70-year-old male patient diagnosed with acute kidney injury accompanying the dialysis requirement. Only acute tubulointerstitial nephritis was revealed in kidney biopsy without evidence of glomerular injury. Also, interstitial pulmonary fibrosis was determined on computerized tomography, and myeloperoxidase antineutrophil cytoplasmic autoantibody was positive. Consequently, we have considered the main diagnosis as MPA. We did not prefer a standard tubulointerstitial nephritis treatment regimen due to the presence of life-threatening systemic vasculitis. Treatment was established like crescentic glomerulonephritis. Induction therapy consisted of pulse steroid, cyclophosphamide, and plasmapheresis. Unfortunately, severe SARS-CoV-2 infection caused death during induction therapy in this case. CONCLUSIONS: The lack of glomerular injury and solely interstitial inflammation is atypical regarding AAV involvement in the kidney. This diversity might be initially considered as only a simple histological elaboration. However, it is a significant entity for guiding the treatment of AAV.

Acute kidney injury in patients with COVID-19: Epidemiology, pathogenesis and treatment.

Acute kidney injury occurs in about 30% of patients hospitalized with coronavirus disease 2019 (COVID-19) and is one of the most common extrapulmonary complications of this disease. The highest risk of acute kidney injury is found in hospitalized patients who require mechanical ventilation. The pathogenesis of acute kidney injury in COVID-19 is multifactorial and seems to not be fully understood. Both direct and indirect mechanisms of kidney injury caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) should be considered. The histological picture of kidney specimens obtained from patients with acute kidney injury in the course of COVID-19 is dominated by acute tubular necrosis. Some patients also have acute interstitial nephritis, blood clots in the kidney vessels and focal segmental glomerulosclerosis (the variant with collapsing vascular loops). Acute kidney injury in COVID-19 is primarily caused not by direct viral effect, but by indirect pathophysiological mechanisms. The histopathological findings in these patients does not differ from the majority of the other patients with acute kidney injury. The main pathophysiological mechanisms underlying acute kidney injury in COVID-19 are: hemodynamic abnormalities, hypoxia and cytokine storm. The methods of treating the underlying disease, i.e., COVID-19 in patients with acute kidney injury and those without acute kidney injury are similar. However, it should be stressed that in the treatment of COVID-19 accompanied by acute kidney injury, the contraindication to remdesivir is estimated using glomerular filtration rate (eGFR) <30 mL/min/1.73 m2. The general principles of management in patients with both, COVID-19 and acute kidney injury do not differ from the principles of management in patients with acute kidney injury due to the other causes.

COVID-19 pneumonia in a kidney transplant recipient successfully treated with tocilizumab and hydroxychloroquine.

Coronavirus disease 2019 (COVID-19) pneumonia has been poorly reported in solid organ transplanted patients; prognosis is uncertain and best management unclear. We describe the case of a 61-year-old kidney transplant recipient with several comorbidities who was hospitalized and later received a diagnosis of COVID-19 pneumonia; the infection was successfully managed with the use of hydroxychloroquine and a single administration of tocilizumab, after immunosuppression reduction; the patient did not require mechanical ventilation. During the rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, transplant clinicians should be readily informed about new cases of COVID-19 pneumonia in solid organ transplant recipients, with focus on therapeutic strategies employed and their outcome.