BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a genetic disorder with uncontrolled complement activation leading to systemic thrombotic microangiopathy; kidneys are almost invariably involved. Eculizumab has dramatically improved the prognosis of aHUS and affected women in the childbearing age are more likely to consider pregnancy, even if this could represent a risk for disease reactivation. Pregnancies in women with aHUS during Eculizumab treatment have been reported, with no cases of aHUS relapse.

CASE REPORT: We report the case of a female patient affected by aHUS with no specific gene mutations who had a pregnancy-associated aHUS relapse at 26-weeks of gestation during maintenance Eculizumab treatment. The patient developed stage II acute kidney injury and microangiopathic hemolytic anemia. Delivery by cesarean section at week 27, plasma exchange sessions and several supplemental Eculizumab administrations were required. After appropriate treatment, the patient partially recovered kidney function; the baby had a prolonged stay in the intensive care unit and showed no signs of neurologic damage.

CONCLUSIONS: Previous reports indicated that pregnancy-related aHUS relapses were unlikely in women undergoing Eculizumab treatment. Based on our case, we suggest caution in counselling pregnancy in women with aHUS treated with Eculizumab, especially in the absence of pathogenic mutations in complement-regulating genes. Clinicians should be aware of possible aHUS relapse in pregnancy during Eculizumab treatment.

Keywords: Complement Inactivating Agents, Hemolytic-Uremic Syndrome, Pregnancy