Case Report: Differential diagnosis and clinical management of isolated prolonged activated partial thromboplastin time.

An unexpected, isolated prolongation of activated partial thromboplastin time (APTT) frequently poses diagnostic challenges in coagulation laboratories. This article presents two patients exhibiting isolated prolonged APTT, one with significant bleeding manifestations and another without bleeding symptoms. The first patient was diagnosed with acquired hemophilia A (AHA), whereas antiphospholipid antibodies (aPLs) were suspected to be responsible for the isolated prolonged APTT in the second patient. Accurate identification of the underlying cause of isolated prolonged APTT is crucial for proper diagnosis and subsequent therapeutic management. Furthermore, we summarize potential causes of isolated prolonged APTT and propose a simplified diagnostic algorithm to distinguish between lupus anticoagulants (LA) (more common) and coagulation factor deficiencies (less common). This report aims to provide insights into the clinical management of similar cases in the future.