Table 1.

Characterization of hemophilia disease severity.^1,2 .

Hemophilia severity	Clotting factor level	Spontaneous bleeding in the absence of prophylaxis	Prophylaxis to prevent bleeding	Eligible for gene therapy clinical trials
Severe	<1 IU/dL	Frequent	Yes	Yes
Moderate	1–5 IU/dL	Occasional	Yes, depending on bleeding phenotype	Yes, if clotting factor level 1–2 IU/dL
Mild	5–40 IU/dL	Rare	Yes, depending on bleeding phenotype	No
Normal	>40 IU/dL	No	No	No

IU/dL, international units per deciliter.