Genetic testing of complement and coagulation pathways in patients with severe hypertension and renal microangiopathy

A diagnosis of thrombotic microangiopathy on kidney biopsy in a patient presenting with hypertensive emergency has historically elicited the diagnosis of malignant hypertension-associated thrombotic microangiopathy. Recent studies, however, have raised awareness that a number of these patients may actually represent atypical hemolytic uremic syndrome. To further investigate this premise, we performed next-generation sequencing to interrogate the coding regions of 29 complement and coagulation cascade genes associated with atypical hemolytic uremic syndrome in 100 non-elderly patients presenting with severe hypertension, renal failure and a kidney biopsy showing microangiopathic changes limited to the classic accelerated hypertension-associated lesion of arterial intimal edema ('mucoid intimal hyperplasia') in isolation and without accompanying glomerular microthrombi. No pathogenic or likely pathogenic variants were identified in any of the genes analyzed, although 13 patients had rare variants of uncertain significance predicted to be deleterious by all in-silico prediction methods utilized. Accordingly, this large patient cohort showed no definitive burden of disease secondary to genetic variants involving complement or coagulation pathways, which contrasts sharply with the high frequency of similar mutational events reported for atypical hemolytic uremic syndrome. Our results also inform recent data by suggesting that patients who present with severe or malignant hypertension and renal thrombotic microangiopathy may be at higher risk for atypical hemolytic uremic syndrome only if the biopsy shows more active disease that includes glomerular fibrin thrombi.