Clinicopathological features and outcomes of glomerular microangiopathy: a retrospective cohort study

Glomerular microangiopathy (GMA) is a group of diseases characterized pathologically by thrombotic microangiopathy (TMA) changes in the glomerulus without detectable microthrombi or intima edema of small arteries on renal biopsy. Few studies have focused on the clinicopathological characteristics and prognosis of patients with GMA. In this single-center retrospective cohort study, we summarized the clinical and pathological data of patients diagnosed with GMA between January 2005 and July 2023 at the Peking Union Medical College Hospital. Treatment and prognosis were also analyzed. A total of 32 patients diagnosed with GMA were included in this study. They were 62.5% male, with a mean age of 46 ± 17 years. The most common primary diseases were idiopathic multicenter Castleman disease (iMCD) (31.2%), POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, and skin changes) syndrome (21.9%), and exposure to anti-vascular endothelial growth factor (VEGF) agents (21.9%). All the patients exhibited various degrees of proteinuria (2.22 g/d (IQR 0.94, 3.50)). Acute kidney injury (AKI) complicated by significantly elevated inflammatory markers was observed in 13 patients, mostly iMCD patients (n = 8). In renal pathology, patients with iMCD showed marked endothelial cell proliferation, whereas patients with POEMS syndrome displayed prominent mesangial cell proliferation. Treatments targeting primary diseases could improve proteinuria and renal function. Patients with GMA primarily presented with proteinuria and AKI. The common primary diseases included iMCD, POEMS syndrome, and exposure to anti-VEGF agents. GMA usually responds well to treatment of primary diseases. Renal pathology is essential for diagnosis. It is important to distinguish GMA from TMA that may respond to anti-C5 therapy.