Other Structural Variants

Hemoglobin C: HbC is a beta globin gene variant. Glutamic acid in the 6th position of the beta chain is replaced by lysine. Red Blood cells containing HbC are more rigid than normal.

Genotypes: HbAC, HbCC, HbC-beta, HbC/HPFH

Hemoglobin D: HbD is a beta globin gene variant. Hemoglobin D-Punjab, D los-Angeles are identical. In both types there is substitution of glutamic acid for lysine.

Genotypes: Hb D-Punjab/Beta Thal, Hb D-Punjab Trait

Hemoglobin O Arab: HbO is a beta globin chain variant. Glutamic acid in 121st position is replaced by glutamine due to point mutation.

Genotypes: Hb O Arab Trait, Hb O Arab Beta Plus or Beta 0.

Hemoglobin E: E Beta Thalassemia: Hemoglobin E is one of the most common abnormal hemoglobins. It is usually found in people of Southeast Asian ancestry, such as Cambodians, Vietnamese and Thai. When combined with beta thalassemia, hemoglobin E produces E beta thalassemia, a moderately severe anemia which is similar in symptoms to beta thalassemia intermedia.

Hemoglobin G Philadelphia: HbG is an alpha chain variant. Two different mutations are reported. Substitution of Asparagine for lysine in 68th position of alpha chain.

Hereditary persistent fetal Hemoglobin (HPFH)

It results from complete absence of beta and delta chain.
It was first described in West Africa in Jamaican family.
HPFH results due to mutation within beta globin cluster that alters normal Hb switching.

Hereditary persistent fetal Hemoglobin (HPFH) Types

Pan cellular HPFH
Heterocellular HPFH

Pan cellular HPFH: HbF is distributed uniformly.
Heterocellular HPFH: HbF is distributed heterogeneously.

Genetics

Two different molecular mechanisms can result in HPFH
Deletional HPFH: Result from specific large deletion in beta globin gene cluster involving HBB
Non Deletional HPFH: Result from point mutation in the promoter of gamma globin gene HBG1, HBG2.