#4808 DIFFERENTIATING POSTPARTUM HELLP SYNDROME FROM ATYPICAL HEMOLYTIC UREMIC SYNDROME

Abstract

Abstract Background and Aims HELLP (hemolysis, elevated liver enzymes, low platelets) is a severe variant of preeclampsia whose pathogenesis remains unknown but likely involves abnormal placentation, endothelial dysfunction and release of vasoactive substances. Complement dysregulation is implicated in the pathogenesis of atypical hemolytic uremic syndrome (aHUS) and there is growing evidence to support its role in HELLP syndrome. Here we present a case of postpartum thrombotic microangiopathy (TMA) in the setting of HELLP syndrome. Method We present a case report. Ethics approval was obtained by the Queen's University Health Sciences and Affiliated Teaching Hospitals Research Ethics Board. Results A 22 year old G1P1 Caucasian woman presents at 37 weeks gestation with abdominal pain and severe hypertension. Labs demonstrated TMA including hemoglobin 95, platelets 30, LDH 2597, and schistocytes. She had severe transaminitis with AST 1845 and ALT 830, and proteinuric acute kidney injury. She was diagnosed with HELLP syndrome and treated with anti-hypertensives and emergency Caesarean section. Unfortunately, the infant did not survive, and there was no placental abruption. Platelets recovered by day 5 postpartum, LDH by day 7. However, renal function worsened and by day 6 postpartum, she required hemodialysis. A renal biopsy revealed acute and chronic TMA. She did not have cortical necrosis. Further workup revealed normal C3, C4 and ADAMTS13 levels. Dialysis was stopped after two weeks. By 6 months, her renal function and proteinuria returned to normal. Complement function testing revealed negative complement factor H autoantibody, but elevated soluble C5b-9 (sC5b-9) level (0.42 mg/L, normal <0.3). Ex-vivo serum C5b-9 deposition on human microvascular endothelial cells was assessed both on resting (182%, normal <150%) and on ADP-activated endothelial cells (273%, normal <150%). This test was repeated 6 months postpartum when renal function had normalized, and results were persistently abnormal both on resting (215%, normal <150%) and on ADP-activated endothelial cells (282%, normal <150%). aHUS genetic testing was negative. Conclusion Results from Burwick et al suggest that this patient had a very high likelihood of clinical aHUS in association with HELLP syndrome (elevated LDH >1832 U/L and creatinine >1.9 mg/dL) [1]. Identifiable aHUS genetic mutations only occur in 50% of aHUS patients. Complement function testing is not routinely assessed for postpartum HELLP; however, the severity of her HELLP syndrome prompted further investigation (C5b-9 deposition testing). The persistence of increased C5b-9 deposition 6 months postpartum for this patient mimics the findings of patients who have confirmed aHUS [2]. Our patient's unique results suggest the patient may be at risk for recurrent TMA/aHUS in her lifetime, particularly if another pregnancy is being considered. Future research should explore which pregnancy associated TMA patients may benefit from anti-complement therapy.