Prekallikrein deficiency

Nurses often encounter abnormal laboratory assays that require them to investigate further to ensure that appropriate patient care is provided. A prolonged activated partial thromboplastin time (PTT) with a normal prothrombin time (PT) assay demand further examination, to rule out laboratory error or bleeding disorders. Prekallikrein deficiency is a rare coagulation deficiency that presents itself with a prolonged PTT and a normal PT. It was first identified in 4 of the 11 Fletcher family children in 1965, coincidentally when one of the Fletcher children was undergoing a workup for an adenoidectomy. Both the Fletcher parents had normal coagulation laboratory assays with no history of bleeding tendencies. The term Fletcher factor deficiency was used until Fletcher factor was later identified as plasma prekallikrein. A prekallikrein deficiency is inherited as an autosomal recessive trait. The purpose of this article is to provide a basic review for nurses on hemostasis, identify the 6 causes of a prolonged PTT with a normal or slightly prolonged PT, and to present 2 recently diagnosed adult cases, not previously reported in the medical literature.