Alpha thalassemia

**Inclusion terms:** - Alpha thalassemia major - Hemoglobin H Constant Spring - Hemoglobin H disease - Hydrops fetalis due to alpha thalassemia - Severe alpha thalassemia - Triple gene defect alpha thalassemia

**Excludes1:** - alpha thalassemia trait or minor (D56.3) - asymptomatic alpha thalassemia (D56.3) - hydrops fetalis due to isoimmunization (P56.0) - hydrops fetalis not due to immune hemolysis (P83.2)

**Use additional code:** - code, if applicable, for hydrops fetalis due to alpha thalassemia (P56.99)