Differential Diagnosis for Isolated Raised aPTT
Single Most Likely Diagnosis
- Lupus Anticoagulant: This is often the most common cause of an isolated prolonged aPTT. Lupus anticoagulant is an antibody that interferes with the coagulation pathway, leading to an increased aPTT. It is associated with autoimmune disorders, such as systemic lupus erythematosus, but can also be found in individuals without a clear autoimmune disease.
Other Likely Diagnoses
- Heparin Therapy: Unfractionated heparin and, to a lesser extent, low molecular weight heparin can cause an isolated prolongation of the aPTT. This is a common and expected side effect of heparin therapy.
- Factor Deficiencies (Factor VIII, IX, XI, XII): Deficiencies in these factors can lead to an isolated prolongation of the aPTT. Factor XII deficiency is particularly known for causing a prolongation of the aPTT without an increased risk of bleeding.
- Von Willebrand Disease: While primarily associated with abnormalities in von Willebrand factor, which can affect the bleeding time and factor VIII levels, some types of von Willebrand disease can present with an isolated prolonged aPTT.
Do Not Miss Diagnoses
- Disseminated Intravascular Coagulation (DIC): Although DIC typically presents with both prolonged PT and aPTT, early stages or specific subtypes might present with an isolated prolongation of the aPTT. Missing DIC can be catastrophic due to its high mortality rate if left untreated.
- Sickle Cell Disease: Certain hemoglobinopathies like sickle cell disease can occasionally present with coagulation abnormalities, including an isolated prolonged aPTT, due to chronic hemolysis and its effects on the coagulation system.
Rare Diagnoses
- Factor VII Deficiency with aPTT Prolongation: While factor VII deficiency typically prolongs the prothrombin time (PT), rare cases might also affect the aPTT, especially if there's a significant deficiency.
- Paroxysmal Nocturnal Hemoglobinuria (PNH): PNH can lead to complement-mediated lysis of red blood cells and occasionally affect the coagulation pathway, potentially causing an isolated prolongation of the aPTT.
- Antiphospholipid Syndrome without Lupus Anticoagulant: Although less common, other antiphospholipid antibodies not classified as lupus anticoagulant can interfere with coagulation tests, leading to an isolated prolonged aPTT.