Pericardial effusion in anti-complement factor H antibody-associated atypical hemolytic uremic syndrome: two case reports.

Hemolytic uremic syndrome (HUS), a cause of pediatric acute kidney injury (AKI), has a spectrum of extra-renal manifestations. While neurological and gastrointestinal system involvement is common, cardiac involvement is rare. This is more so with pericardial involvement, though it has been reported in a handful of HUS cases associated with shiga toxin-producing Escherichia coli (STEC HUS). However, this complication has scarcely been reported in atypical HUS (aHUS) where there is alternate complement abnormality or DKGE (diacylglycerol kinase epsilon) mutation. We describe two children diagnosed with anti-complement factor H (CFH) antibody-associated aHUS who had pericardial involvement. Two boys, one 10-year-old and another 8-year-old, presented with pallor, oliguria and hypertension. They both had microangiopathic haemolytic anemia, thrombocytopenia and AKI suggestive of HUS. Complement workup revealed elevated anti-CFH antibody titres. With a diagnosis of anti-CFH antibody aHUS, they were started on plasmapheresis, pulse methylprednisolone and cyclophosphamide. The first case developed cardiac tamponade during the second week of hospital stay for which he needed pigtail drainage and further immunosuppression with rituximab. He gradually improved and pigtail was removed. The second case presented with pericardial effusion which subsequently resolved during the course of treatment. Thus, our patients developed pericardial effusion, with one of them progressing to life-threatening cardiac tamponade. Therefore, it is prudent that we are aware of this complication while treating children with aHUS.