malignant hypertension ( mhtn ) is characterized by severe hypertension and acute multi - organ ischemic complications including thrombotic microangiopathy ( tma ) . renal thrombotic microangiopathy occurring with mhtn is associated with thrombosis of small vessels , intravascular hemolysis with red cell fragments ( schistocytes ) , platelet consumption and elevated lactic dehydrogenase ( ldh ) levels . there may be associated oliguric acute kidney injury ( aki ) which may rarely require renal replacement therapy for a variable period of time . because of the rarity of renal tma complicating mhtn , its clinical - pathologic features and predictors of renal prognosis are largely unknown [ 18 ] . the renal tma complicating mhtn may itself resemble thrombotic thrombocytopenic purpura ( ttp ) , but distinguishing these two entities is important because of therapeutic implications [ 9 , 10 ] . plasmapheresis is beneficial in ttp , but of no benefit in tma associated with mhtn . herein , we report two cases of mhtn with biopsy - proven renal tma , with prolonged anuria requiring dialysis , but one patient recovered renal function after 9 months . we provide a clinic - pathologic correlation of mhtn in association with tma based on follow - up biopsy findings . a 28-year - old black patient was admitted to hospital with headache , nausea and vomiting and an initial blood pressure ( bp ) of 218/120 mmhg . physical examination showed hypertensive retinopathy with flame - shaped hemorrhages and exudates , but no papilledema . he had a serum creatinine level of 4 mg / dl ( 264 mol / l ) , hemoglobin of 108 g / l and platelet count of 71 000 . over a 4-day period , the bp was decreased to 140/92 mmhg using amlodipine ( 10 mg ) , furosemide ( 80 mg / day ) , minoxidil ( 10 mg / twice daily ) , metoprolol ( 100 mg / day ) and hydrallazine ( 50 mg / every 8 h ) , but the oliguric aki persisted with an increase in creatinine to 1144 mol / l . there was evidence of hemolysis with schistocytes on peripheral smear , high ldh , and low haptoglobin . serologic data such as anti - nuclear antibody , hepatitis b and c , c3 , c4 , human immunodeficiency virus ( hiv ) were all negative . the rest of the clinical data renal biopsy showed fibrinoid necrosis of arterioles and arteriolar thrombosis ( see figure 1 ) . he remained dialysis - dependent for 9 months after which oliguria resolved and creatinine improved to 167.2 mol / l . hemodialysis was stopped and he continues to be followed up in a renal clinic . 
 table 1.laboratory data on two patients with mhtn & tmaclinical datamr amr bmap158180initial creatinine13.49.5peak creatinine13.411.1platelet count85 00040 000platelet nadir71 00029 000ldh13921352haptoglobin<3069egfr ( admission)5.08.0adamts135770bilirubin1.02.4urine protein32547urine creatinine84139urine rbc2510renin38.546.5aldosterone3615pt15.113.3ptt31.829inr1.21fibrinogen423338reticulocyte count3.41.9hivnon - reactivenon - reactivehepatitis panelnegativenegativedirect antithrombinnegativenegativehemodialysis9 monthson going 
 fig . laboratory data on two patients with mhtn & tma case # 2 : a 36-year - old black patient presented to the hospital with dyspnea , headache and visual blurring , and with a bp of 230/130 mmhg . the blood urea nitrogen was 105 mg / dl and creatinine peaked at 11 mg / dl ( 968 mol / l ) . serologic data for antinuclear antibodies , anti - double stranded dna ( ant - dsdna ) , anti scl-70 and other sclerodermal serologies were negative . the patient had evidence of hemolysis with high ldh and low platelets . over a 3-day period , his bp control improved to 130 mmhg/80 mmhg using a similar five - drug regimen . however , he required hemodialysis , since oliguric aki persisted and a kidney biopsy was done . the biopsy showed arteriolar hyalinosis and onion - skin type changes similar to sclerodermal kidneys . this patient has remained dialysis - dependent with irreversible chronic kidney disease for 2 years . oliguric aki persisted for 9 months in case # 1 and irreversible in case # 2 . repeat biopsies ( figure 2a and b ) showed persistent renal tma in case # 2 , but resolution in case 1 . ( b ) persistent tma in glomerulus in patient who did not recover ( 400 ) . ( a ) fibrosis in interstitium and persistent tma in ( b ) . ( b ) persistent tma in glomerulus in patient who did not recover ( 400 ) . tma describes a pathologic process of microvascular thrombosis , thrombocytopenia , microangiopathic hemolysis and end - organ dysfunction . the combination of mhtn and renal tma is rare and 10 other reports of this syndrome have been reported in the literature . renal dysfunction with persistent aki is an important cause of morbidity and mortality in mhtn [ 1113 ] . the prevalence of the combination of tma and mhtn has been variously reported as 44% by akimoto et al . , while van den born reported a prevalence of 27% . the findings on repeat biopsy are quite striking because in patient # 1 , there has been resolution of glomerular and arteriolar evidence of tma , whereas these changes are persistent in case # 2 . persistent tma in case # 2 was associated with endothelial damage , fibrinoid necrosis and an obliterative vasculopathy which may explain persistence of kidney failure with dialysis - dependence . the precise pathogenesis of tma occurring in the setting of mhtn is unknown , but an association between renin - angiotensin system activation has been suggested . another study has suggested that aldosterone level rather than renin activity correlated better as an indicator of vascular injury in mhtn . similarly , the relationship between renal prognosis and tma when this occurs with mhtn has been a source of controversy . distinguishing between the mhtn with aki and tma from ttp is difficult due to significant overlap of presentation [ 710 ] , although this has major therapeutic implications as plasmapheresis has a dramatic beneficial effect in ttp , but has no benefit in mhtn with tma . in ttp , there is a congenital or acquired deficiency of adamts13 , a zinc - containing enzyme that cleaves large von willebrand factor ( vwf ) multimers , thereby decreasing their thrombogenicity . recently , it has been shown that there is an association between tma and reduced adamts13 activity in malignant hypertension . in one report , a low adamts 13 level was suggested as a possible beneficial guide to possible need for plasmapheresis . while some studies suggest resolution of aki resulted from resolution of tma and tubular necrosis lesions , others suggest that tma lesions were associated with greater likelihood of renal recovery . mhtn may be associated with tma and persistent aki with prolonged need for renal replacement therapy.good blood pressure control leads to resolution of hemolysis and thrombocytopenia , although aki may persist for a variable period.use of ace- inhibitors and vasodilators are beneficial in this setting.plasmapheresis is not necessary unless severe thrombocytopenia ( < 25 000/mm ) or severe deficiency of adamts13 is documented . mhtn may be associated with tma and persistent aki with prolonged need for renal replacement therapy . good blood pressure control leads to resolution of hemolysis and thrombocytopenia , although aki may persist for a variable period . plasmapheresis is not necessary unless severe thrombocytopenia ( < 25 000/mm ) or severe deficiency of adamts13 is documented .
two cases of malignant hypertension presenting with acute kidney injury , thrombocytopenia and hemolytic anemia are presented . in both 
 patients a prolonged duration of renal replacement therapy was required . 
 the plasma levels of adamts13 enzyme were not helpful in delineating the precise pathogenesis in both cases , as the decrements were not severe . 
 we discuss the clinic - pathologic correlation of the biopsy findings and persistence of aki .