#5990 COMPLEMENT GENES PROFILE OF PATIENTS WITH SEVERE HYPERTENSION AND RENAL THROMBOTIC MICROANGIOPATHY

Abstract Background and Aims Hereditary or acquired complement system dysregulation found to be driving cause of endothelial damage in atypical haemolytic uremic syndrome (aHUS) – ultrarare life-threatening disease, that always manifests with renal thrombotic microangiopathy (TMA), resulting in poor outcome in absence of appropriate treatment. Nevertheless, several studies show high incidence of rare genetic variants of complement system in other TMA’s, including hypertension-induced TMA. Here we report results of complement genes screening in patients (pts) with histologically identified renal TMA and severe hypertension in Russia, at first diagnosed as hypertension-induced TMA. Method A total of 28 Caucasian pts diagnosed with renal TMA (confirmed by kidney biopsy in all cases) and severe hypertension enrolled in the study. The main characteristic of the clinical picture was the absence of microangiopathic hemolysis and thrombocytopenia in prevailing of the pts, thus most of the primary and secondary causes of TMA clinically excluded. Examination of DNA samples was performed in all pts using next generation sequencing (NGS) technology. For statistical analysis continuous variables were presented as Mean (±Standart deviation) or Median (interquartile range) as appropriate. Results Baseline demographic and clinical characteristics of group are listed in Table 1. 13 pts (46%) had malignant form of hypertension (MHT) confirmed by eye examination. Mean systolic arterial pressure (SAP) observed at the time of presentation was 210±29 mmHg, mean diastolic arterial pressure (DAP) was 122±19 mmHg. Kidney morphology revealed chronic TMA lesions in 12 pts (43%), acute and chronic alterations simultaneously detected in 13 pts (46%). Predominantly acute lesions with glomerular and extraglomerular thrombi found in 3 (11%) pts only. Complement genes abnormalities revealed in 7 (25%) out of 28 pts. Complement factor I (CFI) rare variants were found in 2 pts (CFI c. 772<A, CFI c.1217G>A), one of this pts also had additional variant in complement factor H related protein 4 (CFHR4 c.766G>A). Complement factor C3 rare variant was observed in 1 pt (C3 c.2203C>T), membrane cofactor protein (MCP or CD46) rare variant in 1 pt (CD46 c. 198A>T), complement factor H related protein 5 (CFHR5) variant detected in 1 pt (CFHR5 c.136C>T), homozygous deletion of CFHR1 and CFHR3 detected in 1 pt and heterozygous deletion of the same complement factor H related protein genes found in another pt. Conclusion A quarter of pts with TMA and severe hypertension may have genetic defects in the complement system. These results confirmed that complement-mediated HUS may be misdiagnosed as hypertension-induced TMA. Lack of convincing hematological signs of TMA is common in this group, making aHUS diagnosis more sophisticated.