Examples of genotype and phenotype correlation in thalassemia - McMaster Textbook of Internal Medicine

Table 9.1-1. Examples of genotype and phenotype correlation in thalassemia
	Phenotype	Genotype	Clinical manifestations
Beta thalassemia	Trait/minor	Beta/beta+	Mild microcytic anemia
	Intermedia (non–transfusion-dependent thalassemia)	Beta+/beta0 Beta+/beta+	Moderate to severe microcytic anemia
	Major (transfusion-dependent thalassemia)	Beta0/beta0	Severe anemia; transfusion-dependent
Alpha thalassemia	Carrier	-alpha/alpha alpha	Asymptomatic; MCV normal or mild microcytosis
	Trait/minor	--/alpha alpha -alpha/-alpha	Mild anemia with microcytosis
	Hemoglobin H disease	--/-alpha	Mild to moderate microcytic anemia
	Bart hydrops fetalis	--/--	May be fatal in utero or neonatal period
-, loss of alpha chain; alpha, functional alpha chain; beta0, no beta-globin chain production; beta+, reduced beta-globin chain production; MCV, mean corpuscular volume.