Atypical hemolytic uremic syndrome (aHUS), caused by defects in the alternative complement pathway or its regulatory proteins, is a rare condition that can present in life-threatening episodes, especially when triggered by stressors such as infection or pregnancy. This case underscores the importance of rapid identification and intervention in aHUS, especially in high-risk contexts.
We present a 19-year-old pregnant woman at 37 weeks gestation brought to the ER unresponsive, with agonal breathing and seizures. She had last been seen the day prior and was complaining of abdominal pain. After undergoing emergency C-section for intrauterine fetal demise, she was transferred to the intensive care unit. Physical exam revealed the patient was obtunded with flaccid extremities and absent reflexes. Initial labs showed hyponatremia, leukocytosis, acute kidney injury, severe thrombocytopenia, and microangiopathic hemolytic anemia. Brain imaging suggested anoxic brain injury and EEG showed severe diffuse encephalopathy with no epileptiform discharges. Differential diagnoses included thrombotic thrombocytopenic purpura (TTP); disseminated intravascular coagulation (DIC); aHUS; HELLP (hemolysis, elevated liver enzymes and low platelets); and catastrophic antiphospholipid syndrome. The patient received hemodynamic support, mechanical ventilation, broad-spectrum antibiotics, high-dose corticosteroids, blood transfusions, and plasmapheresis. The patient’s clinical status improved significantly within 24 hours, regaining consciousness and reflexes, and was extubated within 72 hours. An ADAMTS13 of 38% ruled out TTP. Given high suspicion for HELLP versus aHUS, she received meningococcal vaccination and penicillin prophylaxis before initiating eculizumab. Genetic testing ultimately confirmed aHUS with two heterozygous gene defects in complement proteins, CD46 and CFHR3-CFHR1. The patient continued eculizumab and later transitioned to ravulizumab for maintenance therapy for 6 months. She returned to her neurological baseline without end-organ damage and received therapy for postpartum depression and contraception counseling for one year.
This case highlights the remarkable recovery that patients with aHUS can experience when treatment is quickly initiated when a high index of suspicion exists. Emphasis on genetic evaluation can provide valuable information regarding probability of relapse or end-stage renal disease. Children should also be tested for complement dysregulation if maternal HUS occurred during pregnancy or postpartum without a clear secondary cause.
