The mother of a 4-year-old boy brings her son to his pediatrician for a repeated episodes of easy bruising and epistaxis. Blood work reveals a prolonged PTT, a normal PT, and a prolonged bleeding time. Platelet count is 285,000/uL. Based on these laboratory findings, what is the most likely diagnosis?

Question

Quizplus · Accepted Answer

The laboratory findings of prolonged PTT, normal PT, prolonged bleeding time, and normal platelet count are consistent with von Willebrand disease, which affects both platelet function and the intrinsic coagulation pathway.  Partial thromboplastin time (PTT), prothrombin time (PT), bleeding time, and platelet count are key laboratory tests used to differentiate between bleeding disorders. PTT measures plasma clotting time to assess the integrity of the intrinsic coagulation pathway (factors XII, XI, IX, VIII, X, V; prothrombin; and fibrinogen). PT measures plasma clotting time to assess the integrity of the extrinsic pathway (factors VII, V, X; prothrombin; and fibrinogen). Bleeding time measures the time needed for a standard skin puncture to stop bleeding and assesses platelet ability to form a hemostatic plug. von Willebrand disease results from deficiencies in both factor VIII and in von Willebrand factor (vWF), which combine to form a circulating complex. Synthesized by endothelial cells, vWF is important in the facilitation of platelet adhesion to subendothelial collagen. As a constituent in the factor VIII-vWF circulating complex, it serves to stabilize factor VIII and significantly increase its half-life; thus, a deficiency in vWF will cause a secondary decrease in factor VIII levels. von Willebrand disease demonstrates autosomal dominant inheritance and is believed to be one of the most common inherited bleeding disorders. Patients show bleeding after minor trauma, with the most common sites including skin (easy bruising) and mucous membranes (epistaxis). Coagulation tests reveal a prolonged PTT, a normal PT, and a prolonged bleeding time with normal platelet count.

The Mother of a 4-Year-Old Boy Brings Her Son to His