posterior reversible encephalopathy syndrome ( pres ) is a clinico - radiological syndrome , comprising symptoms such as headache , seizures , visual disturbances , lethargy , confusion , stupor , and focal neurologic findings . in addition , radiological findings of bilateral gray and white matter abnormalities suggestive of edema in the posterior regions of the cerebral hemispheres are essential for the diagnosis . since hinchey et al first reported , pres has been seen in various clinical settings , including renal disorders such as acute glomerulonephritis , lupus nephritis , and nephrotic syndrome [ 3 , 4 ] . the two theories regarding the pathophysiology of onset of vasogenic edema are hyperperfusion due to autoregulatory failure of the cerebral vasculature and hypoperfusion due to vasoconstriction of the cerebral artery . when blood pressure exceeds a certain set point in cases of significant systemic hypertension , autoregulation failure may occur . this results in cerebral hyperperfusion and breakdown of the blood - brain barrier , which in turn lead to vasogenic edema . pres is a relatively in the renal desorders but potentially a serious complication . in this report , we present two patients with pres in whom the primary diagnosis was hemolytic uremic syndrome ( hus ) and henoch - schonlein purpura ( hsp ) . a previously healthy 6-year - old girl presented with abdominal pain , vomiting , and macroscopic hematuria . at the time of application , her vital signs except blood pressure were normal . a full blood count revealed anemia ( hg 7.4 g / dl ) and thrombocytopenia ( 42,000/mm ) . blood chemistry results were as follows : serum creatinine 4.6 mg / dl and lactic dehydrogenase ( ldh ) 1,200 iu / l . she was immediately treated with both plasmapheresis and hemodialysis . on the eighth day of her hospitalization , she had a generalized tonic - clonic seizure , became confused and complained of bilateral complete loss of vision . neurologic examination showed normal findings , including her pupillary reflexes to light and normal accommodation . her contrast - enhanced computed tomography showed no abnormality but cranial magnetic resonance image ( mri ) revealed high signal abnormality . brain mri including diffusion - weighted images ( dwi ) showed faint signal intensities on bilateral parietal subcortical white matter without diffusion restriction ( fig . axial flair image ( a ) of case 1 shows faint signal intensities on both parietal white matter . diffusion image ( b ) fails to show any restriction which is consistent with pres . axial flair image ( c ) of case 2 and corresponding dwi image ( d ) show increased signal intensities at bilateral occipital and parietal lobes consistent with pres . a previously healthy 8-year - old girl presented with abdominal pain , hematochezia , rash on her legs , and macroscopic hematuria . with the diagnosis of hsp , she was put on oral prednisolone therapy . on the 10th day of her hospitalization the rest of her physical and neurological examinations and her vital sign were all within normal limits . laboratory findings showed anemia ( hg 9.6 g / dl ) , proteinuria 3 + , and hematuria . renal ultrasonography revealed normal sized , moderately echogenic kidneys ( grade 2 - 3 ) . the renal biopsy due to the underlying hsp nephritic disease stage showed focal necrotizing cresentic glomerulonephritis . due to fourteen days later , she suddenly complained of loss of vision ; thereafter , she had generalized tonic seizure . blood pressure was found to be 130/90 mm hg at the time and amlodipine was started and followed by enalapril and propanolol for persistant hypertension . the contrast - enhanced cranial computed tomography was normal but the cranial mri revealed bilateral hyperintense white matter lesions in the occipital and posterior parietal regions on t2-weighted fluid - attenuated inversion recovery ( flair ) and dwi ( fig . an eeg showed diffuse slow waves at all leads and there were focal isolated temporooccipital sharp wave discharges . a previously healthy 6-year - old girl presented with abdominal pain , vomiting , and macroscopic hematuria . at the time of application , her vital signs except blood pressure were normal . a full blood count revealed anemia ( hg 7.4 g / dl ) and thrombocytopenia ( 42,000/mm ) . blood chemistry results were as follows : serum creatinine 4.6 mg / dl and lactic dehydrogenase ( ldh ) 1,200 iu / l . she was immediately treated with both plasmapheresis and hemodialysis . on the eighth day of her hospitalization , she had a generalized tonic - clonic seizure , became confused and complained of bilateral complete loss of vision . neurologic examination showed normal findings , including her pupillary reflexes to light and normal accommodation . her contrast - enhanced computed tomography showed no abnormality but cranial magnetic resonance image ( mri ) revealed high signal abnormality . brain mri including diffusion - weighted images ( dwi ) showed faint signal intensities on bilateral parietal subcortical white matter without diffusion restriction ( fig . axial flair image ( a ) of case 1 shows faint signal intensities on both parietal white matter . diffusion image ( b ) fails to show any restriction which is consistent with pres . axial flair image ( c ) of case 2 and corresponding dwi image ( d ) show increased signal intensities at bilateral occipital and parietal lobes consistent with pres . a previously healthy 8-year - old girl presented with abdominal pain , hematochezia , rash on her legs , and macroscopic hematuria . with the diagnosis of hsp , she was put on oral prednisolone therapy . on the 10th day of her hospitalization the rest of her physical and neurological examinations and her vital sign were all within normal limits . laboratory findings showed anemia ( hg 9.6 g / dl ) , proteinuria 3 + , and hematuria . renal ultrasonography revealed normal sized , moderately echogenic kidneys ( grade 2 - 3 ) . the renal biopsy due to the underlying hsp nephritic disease stage showed focal necrotizing cresentic glomerulonephritis . due to both renal and gastrointestinal involvement of hsp , prednisolone was started . fourteen days later , she suddenly complained of loss of vision ; thereafter , she had generalized tonic seizure . blood pressure was found to be 130/90 mm hg at the time and amlodipine was started and followed by enalapril and propanolol for persistant hypertension . the contrast - enhanced cranial computed tomography was normal but the cranial mri revealed bilateral hyperintense white matter lesions in the occipital and posterior parietal regions on t2-weighted fluid - attenuated inversion recovery ( flair ) and dwi ( fig . an eeg showed diffuse slow waves at all leads and there were focal isolated temporooccipital sharp wave discharges . for the primary disease of hsp , she was given oral steroid and cyclophosphamide for the last 4 months . although they are completely different diseases with different etiologies , the vascular systems are affected in both diseases and hypertension was the common finding in two children . pres was originally defined in 1996 , with the clinical signs of renal insufficiency , hypertension , or immunosuppressive status , exhibiting headaches , altered mental functioning , seizures , and visual disturbance . the neuroimaging findings were characteristic of posterior brain edema without infarction , suggesting capillary leakage and breakdown of blood - brain barrier . the clinical symptoms and neuroradiological findings of pres are typically indistinguishable , regardless of etiology and underlying factors . beside its specific clinical setting which comprises mostly nephrologic patients to date , there is no evidence supporting genetic susceptibility to pres . although there are some limitations , cranial mri is the gold standard of imaging studies for detecting the lesions of pres . typical cranial images show focal regions of relatively symmetric hemispheric edema and the parietal and occipital lobes are most commonly affected . the differential diagnosis of pres includes cerebral vasculitis , cerebral venous trombosis , encephalitis , hypertensive encephalopathy , cerebral findings secondary to hypoglycemia and hyponatremia . the mainstays of the management of pres are control of blood pressure , treatment of seizures , and removal or reduction of other causative factors . after ruling out cerebral infarction , blood pressure should be lowered to the mean arterial pressure by 25% within the first hour . long - term prognosis is an important issue in children with pres , but evidence is scarce . these may suggest the necessity of long - term follow - up even including those who show complete clinical and radiological recovery in the short term period . subtle neurological disabilities , including subclinical developmental delay and learning problems , are of particular significance in some children . in the literature , there are also some cases diagnosed as hsp and hus [ 8 , 9 ] who developed pres during the natural course of their diseases . our patients demonstrated the characteristic radiologic signs and clinical features of pres , including headache , altered sensorium , seizures and visual disturbances . so that both of them were treated with anticonvulsant and proper antihypertensive drugs . a repeated mri scan of the head , an ophthalmologic assessment , and a follow - up eeg produced normal results with no sequelae . hemodynamic changes due to severe hypertension and renal insufficiency may be involved in the pathogenesis of pres associated with hsp . platelet - fibrin thrombus by occluding predominantly renal but rarely brain vessels subsequently may induce endothelial cell damages . stimulated endothelial cells can produce cytokines and chemokines , i.e. , interleukin-1 , 6 , 8 , tnf - alpha , and von - willebrand factor in situ . these substrates can induce vasospasms in cerebral vessels , which may lead to additional microemboli and breakdown of blood - brain barrier , which resemble to the underlying pathogenesis of pres . although pres was initially supposed to be a reversible and treatable disease , unusual pres cases associated with irreversible brain lesions have been accumulated . however , that was not the case in our patients . clinical symptoms leading to consideration of pres should be first evaluated for the primary disease especially in nephrologic patients and patients with hypertension . afterwards if there is no suspicion of the complication of the primary disease , cerebral infarction and hypertensive encephalopathy , pres should be considered for the diagnosis . in that cases mri becomes important and should be performed without hesitation before the resolution of the edema . morever , the eeg findings also should be assessed , in order to exclude the later development of epilepsy .
posterior reversible encephalopathy syndrome ( pres ) is a clinico - radiological syndrome , composed of symptoms such as headache , seizures , visual disturbances , lethargy , confusion , stupor , focal neurologic findings and radiological findings of bilateral gray and white matter abnormalities suggestive of edema in the posterior regions of the cerebral hemispheres . 
 pres is associated with significant morbidity and mortality if it is not expeditiously recognized . magnetic resonance image ( mri ) 
 represents the most sensitive imaging technique for recognizing pres . 
 pres has been seen in various clinical settings including renal disorders such as acute glomerulonephritis , lupus nephritis , nephrotic syndrome , and drug usage such as calcineurin inhibitors . 
 we aimed to present two study cases for such clinical setting . in this report , we present two patients with pres in whom the primary diagnosis was hemolytic uremic syndrome ( hus ) and henoch - schonlein purpura ( hsp ) . 
 both of them were treated with anticonvulsant and proper antihypertensive drugs . a repeated mri scan of the head , an ophthalmologic assessment , and a follow - up electroencephalogram produced normal results with no sequelae . 
 early recognition of pres as a complication during different diseases and therapies in childhood may facilitate the appropriate treatment , so that intensive treatment should be performed as soon as possible to avoid neurological sequelae .