A clinicopathologic study of thrombotic microangiopathy in the setting of IgA nephropathy

IgA nephropathy is the most common glomerulonephritis in the world. Thrombotic microangiopathy occurs in a number of clinical settings, including but not limited to thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, malignant hypertension, anti-phospholipid antibody syndrome and radiation nephropathy. Renovascular complications, such as thrombotic microangiopathy, in the setting of IgA nephropathy may be overlooked and their significance as a concomitant histologic finding is unclear.

We conducted a clinicopathologic study to understand the possible relationship between IgA nephropathy and a concurrent thrombotic microangiopathy injury process. We identified 10 patients with an established diagnosis of IgA nephropathy and concurrent findings of thrombotic microangiopathy based on their renal biopsies.

Six patients presented with malignant hypertension, while three others had severe hypertension (> or = 100 mmHg, diastolic). Five patients had nephrotic-range proteinuria. Seven patients had occasional arteriolar thrombi identified by light microscopy and prominent glomerular subendothelial space widening by electron microscopy, while three patients demonstrated only ultrastructural features of thrombotic microangiopathy. Other possible etiologic causes of thrombotic microangiopathy were not identified with the available clinical information.

Our study suggests that a thrombotic microangiopathy injury, when present, is usually found in advanced stages of IgA nephropathy and can be associated with severe proteinuria. Although other possible causes of thrombotic microangiopathy, such as anti-phospholipid antibody syndrome, were excluded in only two patients, the thrombotic microangiopathy injury process may be a cause or a consequence of the severe hypertension encountered in most of the patients which, in turn, may be a consequence of the disease progression of IgA nephropathy.