Diagnosis of atypical HUS using Genetic Testing

Abstract

The patient is a 33 year old woman at 31 weeks gestation with twins who presented to the ER complaining of shortness of breath, headache, and blurry vision. The patient’s preliminary complete blood count (CBC), RBC morphology, coagulation testing, and certain metabolic indicators were characteristic of a hemolytic process caused by microcirculatory lesions known as thrombotic microangiopathies. The major pathologies of this hemolytic process are Thrombotic Thrombocytopenic Purpura (TTP), Hemolytic Uremic Syndrome (HUS), Disseminated Intravascular Coagulation (DIC), and Hemolysis, Elevated Liver Enzymes, Low Platelets (HELLP). Additional coagulation and biochemical testing indicated that the patient probably was experiencing HELLP syndrome, but atypical HUS (aHUS) could not be ruled out. Consequently an aHUS genetic susceptibility panel was also ordered on this patient. The results of the genetic testing revealed that the patient did indeed have aHUS. Atypical hemolytic uremic syndrome is a disease of complement dysregulation. In approximately 50% of patients, mutations have been described in the genes that encode complement regulator factors. With an accurate diagnosis established, the patient was able to receive treatment utilizing an anti C5 monoclonal antibody aimed specifically at controlling the dysregulated complement protein C5.