Acquired haemophilia: an overview for clinical practice.

Acquired haemophilia is a potentially life-threatening bleeding disorder caused by the development of autoantibodies against coagulation factors, most commonly against factor (F) VIII (acquired haemophilia A; AHA). In around half of patients, an underlying disorder is associated with AHA; the remaining cases are idiopathic. Typically, the disorder presents with bleeding, ranging from mild to life- and limb-threatening, in patients with no personal or family bleeding history. Diagnosis involves an isolated prolongation of the activated partial thromboplastin time, without correction in mixing studies, low FVIII activity levels and evidence of a FVIII inhibitor. As AHA is rare, a lack of familiarity of the condition may result in delayed diagnosis, and prompt haemostatic control is required to reduce morbidity and mortality. Bypassing agents (recombinant activated factor VII or activated prothrombin complex concentrates) can be used to control acute bleeding, and immunosuppression is necessary to eradicate the inhibitor. As clinical trials in this rare and heterogeneous disease are difficult, current evidence comes from observational studies, including registries. This review will focus on the diagnostic and therapeutic challenges of AHA and summarise how understanding of this complex condition has increased based on recent registry data.