Differential diagnosis and clinical management of isolated prolonged activated partial thromboplastin time in a patient with Hashimoto thyroiditis-associated thyroid cancer

Rationale: Patients preparing for surgery may have isolated, prolonged activated partial thromboplastin time (APTT). Cause analysis is warranted in patients who had neither bleeding symptom nor thromboembolic events because isolated prolongation of APTT may lead to unnecessary delayed surgical intervention or invasive procedure, even ineffective plasma infusion treatments. Here, we report a case of Hashimoto thyroiditis-associated thyroid cancer whose APTT was isolated prolonged and discuss the challenges of diagnosis and clinical management of this patient. Patient concerns: A 57-year-old woman was admitted to the hospital due to thyroid cancer. Anticoagulant assay was performed for this patient before surgery, she had normal values for prothrombin time, thrombin time, and fibrinogen, but had isolated prolonged APTT value (20 seconds longer than normal). However, the routine laboratory of the local hospital showed normal APTT and she did not have any abnormal bleeding or thrombotic episodes. Lupus anticoagulant (LA) was strongly positive according to mixing studies and modified dilute Russell viper venom time method, it was responsible for prolonged APTT. Diagnoses: Hashimoto thyroiditis-associated thyroid cancer whose APTT was isolated prolonged. Interventions: The isolated prolongation of APTT in this patient was due to LA. She had no history of anticoagulant medications and no spontaneous bleeding episodes. There should be no specific intervention before thyroidectomy. Outcomes: This thyroid cancer patient had an uneventful surgery and was discharged after a week. Lessons: Prolonged APTT is not considered an absolute indication for plasma infusion therapy in patients with LA. The correct identification of the cause of APTT prolongation is essential for proper treatment of the individuals.