Differential Diagnosis for a 3-year-old Male with Easy Bruising

Single Most Likely Diagnosis

• Von Willebrand Disease (VWD): This is the most likely diagnosis given the easy bruising and the laboratory results showing a prolonged PTT (33 seconds) and decreased factor 8 activity (47%). VWD is a common inherited bleeding disorder characterized by a deficiency or dysfunction of von Willebrand factor, which is crucial for platelet adhesion and protection of factor VIII from degradation.

Other Likely Diagnoses

• Mild Hemophilia A: Although less likely than VWD due to the specific lab results, mild hemophilia A could present with easy bruising and a decrease in factor VIII activity. However, the PTT might not be as significantly prolonged as in more severe forms.
• Platelet Function Disorders: Disorders affecting platelet function, such as Bernard-Soulier syndrome or platelet storage pool defects, could also present with easy bruising. However, these conditions typically have normal coagulation studies (like PTT) but abnormal platelet function tests.

Do Not Miss Diagnoses

• Acute or Chronic Liver Disease: Liver disease can lead to coagulopathy due to decreased production of clotting factors, including factor VIII. Although less likely given the specific factor VIII activity level, liver disease is a critical diagnosis not to miss due to its potential for severe morbidity and mortality.
• Vitamin K Deficiency: Vitamin K is essential for the production of several clotting factors. A deficiency could lead to easy bruising and coagulopathy, including a prolonged PTT and decreased factor VIII activity. This diagnosis is particularly important in infants and young children with dietary deficiencies or malabsorption.

Rare Diagnoses

• Factor VIII Inhibitors: The development of inhibitors against factor VIII is a rare condition that can occur in individuals with hemophilia A or, more rarely, in those without a history of hemophilia (acquired hemophilia A). This condition would present with bleeding symptoms and a significant decrease in factor VIII activity.
• Glanzmann's Thrombasthenia: A rare bleeding disorder characterized by platelet dysfunction due to deficiencies in glycoproteins IIb/IIIa. While it presents with easy bruising, the coagulation studies (like PTT) are typically normal, making it less likely given the prolonged PTT in this case.