thrombotic microangiopathies result from damage to the endothelium leading to a cascade of thrombosis and resultant anemia , thrombocytopenia , and renal damage . atypical hemolytic uremic syndrome ( ahus ) , a rare genetic disorder of this class stems from a rapid inappropriate activation of the complement system , termed  atypical  due to the lack of a triggering event akin to conventional hus which starts with exposure to the shiga - like toxin . the mortality in pediatric - onset ahus is reported to be more ( 6.7% ) while adult onset has higher chances of progression to end - stage renal disease . newer therapy such as the complement binding antibody eculizumab is financially unviable at present in the indian setting . a 14-year - old male , presented with complaints of sudden reddish discoloration of urine 5 days back followed by yellowing of eyes and skin , nausea , and vomiting associated with feeds . on routine investigation , he was anemic ( hemoglobin 4.9 g% ) with thrombocytopenia ( platelets 97,000 ) . renal functions were deranged with a serum creatinine of 4.27 and blood urea of 116.8 . a peripheral blood smear revealed dimorphic anemia with thrombocytopenia with polymorphonuclear leukocytosis with abundant schistocytes and tear drop cells suggestive of hemolytic uremic syndrome with a reticulocyte count of 30% . anti - nuclear antibodies were absent with low complement 3 ( c3 ) and normal c4 levels . anti - complement factor h ( cfh ) antibodies were found to be significantly raised at 2043 au / ml . he was initiated on plasma exchange with 7 initial daily cycles and a total of 16 cycles titrated to clinical response . anti - cfh antibodies were repeated and found to have decreased to 191.07 au / ml . he later developed sudden onset severe headache followed by loss of vision progressing to generalized tonic he was intubated and later successfully weaned off mechanical ventilation . a magnetic resonance imaging ( mri ) brain revealed posterior reversible encephalopathy with altered signal intensity in a subcortical white matter of the bilateral parietal , occipital , posterior temporal lobes and cerebellar hemispheres [ figure 1 ] . severe skin rashes developed almost 2 months into admission : centripetal in development with mucosal involvement and was diagnosed as steven he was started on further immunosuppression with steroids and azathioprine and discharged on day 91 of admission in complete clinical and hematological remission . ( b ) thermal - infrared images show symmetrical hypointense lesions in bilateral parietal lobes . ( c ) fluid - attenuated inversion recovery hyperintensities in occipital lobe typical of posterior reversible encephalopathy . ahus is a thrombotic microangiopathy resulting from mutations in cfh , complement factor i , membrane cofactor protein ( cd46 ) , c3 , thrombomodulin , cfh - receptor 5 , or from autoantibodies to cfh . autoantibodies to cfh reported in 4%14% of all cases , however , are much more common in cases with early onset of disease and are present in up to 25% of such cases . autoantibodies to cfh prevent cell surface protection by cfh , chiefly by inhibiting binding to c3b . ahus may be suspected in patients with typical history along with proven negative stool cultures for shiga - like toxin and normal adamts13 activity and can be confirmed by genetic assays , though empiric treatment is often initiated . the autoimmune variant , however , as in our case may not have a genetic focus and can be diagnosed by high levels of antibodies to cfh ( 2043 au / ml in our case ) . the overall ahus has incomplete penetrance , and an infectious trigger is often associated with the disease precipitating . our case presented with a high - grade fever of undocumented etiology which was probably the trigger for complement activation . globally , eculizumab , the monoclonal antibody to c5b , has found acceptance in the treatment of ahus . guidelines issued in 2009 recommended initial daily plasma exchange ( 5070 ml / kg ) with further titration of frequency according to clinical response . our patient received an initial seven cycles of daily plasma exchange followed by gradual tapering with monitoring of hematological and renal parameters which showed complete normalization by the 12 cycle . cfh - related ahus , similar to our patient , has been documented to respond better to plasma exchange . our patient did not develop any requirement for renal replacement therapy with hemodialysis as is the norm in a majority of cases of ahus . hypertension is a common complication of ahus but developed late in the course of treatment in our patient . posterior reversible encephalopathy with associated loss of vision may have an identical presentation as cerebral thrombotic microangiopathy . the latter can be differentiated on the basis of asymmetry of the lesions on mri . although neurological sequelae respond best to eculizumab , our patient was already in remission at the time of onset . johnson syndrome was probably a coincidental reaction to phenytoin and does not relate to ahus in the available literature . cyclophosphamide , mycophenolate mofetil , azathioprine and steroids , all have supporting literature for maintenance therapy . 36.5%63% progress to mortality or end - stage renal disease in the long - term . the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s ) has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal . the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed . the authors certify that they have obtained all appropriate patient consent forms . in the form the patient(s ) has / have given his / her / their consent for his / her / their images and other clinical information to be reported in the journal . the patients understand that their names and initials will not be published and due efforts will be made to conceal their identity , but anonymity can not be guaranteed .
atypical hemolytic uremic syndrome ( ahus ) is a rare disorder resulting from a dysregulated activation of the alternative pathway of the complement system . 
 it results in significant morbidity and mortality if not diagnosed and treated promptly . 
 it lends itself to myriad renal and extrarenal manifestations , all potentially disabling . 
 eculizumab , a monoclonal antibody to complement c5 is now the widely accepted norm for treatment . 
 however , in resource - limited settings , plasma exchange if instituted early may be as beneficial . 
 we report a case of ahus treated with extended plasma exchange with excellent results . 
 critical care monitoring is essential for the management of the disease in view of a tendency to develop multiple complications . 
 long - term immunosuppression may be successful in maintaining remission .