Assistant Professor Eastern Virginia Medical School, United States
Introduction: Atypical hemolytic syndrome (aHUS) is a form of thrombotic microangiopathy (TMA) secondary to a genetic cause. Due to the high morbidity and mortality of aHUS, prompt diagnosis and treatment are paramount. Diagnosis may be complicated by testing limitations and clinical prominence of acute kidney injury over thrombotic symptoms. We report a case of aHUS that was initially thought to be progression of chronic kidney disease (CKD).
Description: A 73-year-old female with chronic kidney disease stage V due to ANCA vasculitis, lupus, hypertension presented to the emergency department with oliguria, intractable nausea, dysgeusia, and unintentional weight loss. She had creatinine of 6.1 up from her baseline of 3 with clinical signs of fluid overload. Hemodialysis was initiated due to fluid overload and uremia. She was subsequently discharged home on hemodialysis. She continued to decline despite adherence to dialysis schedule. She was readmitted after four weeks and was found to have thrombocytopenia to 53 K/uL. Additional investigation revealed a haptoglobin < 1 mg/dL, immature platelet fraction of 22.5%, elevated LDH to 211 U/L, normal coagulation panel, negative ADAMTS-13 testing, and schistocytes and decreased platelets seen on peripheral blood smear suggestive of TMA. Daily plasmapheresis (PLEX) was initiated with marked improvement of platelet counts and modest symptom improvement. Her genetic work up returned negative, however, considering her clinical picture and improvement with PLEX, she was diagnosed as a case of aHUS. Eculizumab was initiated and the patient achieved complete resolution of symptoms. On further follow up, her cell counts normalized after four cycles of eculizumab.
Discussion: This case highlights a challenging diagnosis of aHUS in setting of advanced CKD. Acute worsening of CKD V led to initiation of hemodialysis. However, lack of symptom resolution prompted further work up leading to diagnosis of aHUS. This case also highlights current limitations of testing for aHUS. Genetic markers for aHUS have only been identified in 40-60% of diagnosed patients and several variants of unknown significance have been observed. In patients with a high clinical suspicion, treatment directed towards presumptive diagnosis of aHUS may be lifesaving.
