Which von Willebrand disease type is associated with having four subtypes and autosomal dominant inheritance?

Which von Willebrand disease type is associated with having four subtypes and autosomal dominant inheritance?

• A. Type 1
• B. Type 3
• C. Type 2
• D. Type 4

Answer: (C)

The idea being tested is distinguishing von Willebrand disease types by whether the defect is quantitative or qualitative, and how inheritance patterns align with those types. The type that has four subtypes corresponds to a qualitative defect in von Willebrand factor, and it is commonly inherited in an autosomal dominant manner. In this group, the four subtypes—each a distinct functional problem with vWF—explain the four subtypes: one involves loss of the high-midelity multimers necessary for proper platelet adhesion, another shows increased binding of vWF to the platelet receptor leading to premature clearance, a third has a qualitative defect with normal multimer distribution causing reduced platelet-dependent function, and the fourth has defective binding of vWF to factor VIII, lowering FVIII levels. Because these are changes in the function of vWF rather than just how much vWF is present, they fit the pattern of autosomal dominant inheritance, where one mutated copy can produce the disorder. In contrast, Type 1 is a partial quantitative deficiency (reduced amount of vWF) and Type 3 is a severe quantitative deficiency that is typically autosomal recessive. The four-subtype pattern and the dominant inheritance point to the qualitative, Type 2 category.

The idea being tested is distinguishing von Willebrand disease types by whether the defect is quantitative or qualitative, and how inheritance patterns align with those types. The type that has four subtypes corresponds to a qualitative defect in von Willebrand factor, and it is commonly inherited in an autosomal dominant manner.

In this group, the four subtypes—each a distinct functional problem with vWF—explain the four subtypes: one involves loss of the high-midelity multimers necessary for proper platelet adhesion, another shows increased binding of vWF to the platelet receptor leading to premature clearance, a third has a qualitative defect with normal multimer distribution causing reduced platelet-dependent function, and the fourth has defective binding of vWF to factor VIII, lowering FVIII levels. Because these are changes in the function of vWF rather than just how much vWF is present, they fit the pattern of autosomal dominant inheritance, where one mutated copy can produce the disorder.

In contrast, Type 1 is a partial quantitative deficiency (reduced amount of vWF) and Type 3 is a severe quantitative deficiency that is typically autosomal recessive. The four-subtype pattern and the dominant inheritance point to the qualitative, Type 2 category.