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hemoglobin E
Epidemiology:
1) 2nd most prevalent hemoglobin variant worldwide & 3rd in US following Hgb S & C
2) most common in patients of southeast Asian decent
Clinical manifestations:
- no anemia in homozygous state
Laboratory:
1) complete blood count (CBC
a) microcytosis
1] MCV = 67 fl {homozygous}, 73 fl {heterozygous}
2] out of proportion to degree of anemia
b) RDW is generally normal
2) iron studies are generally normal
3) hemoglobin electrophoresis
Properties
GENERAL: hemoglobin-variant
COMPARTMENT: cytoplasm
CELL: erythrocyte
SUBUNITS: hemoglobin alpha chain (2)
MOTIF: lysine residue {12}
lysine residue {57}
Iron [Fe]-binding site
SITE: 59-59
lysine residue {61}
Iron [Fe]-binding site
SITE: 88-88
lysine residue {91}
lysine residue {100}
hemoglobin beta chain (2)
MOTIF: point mutation
SITE: RESIDUE-26
MUTATION-FROM-AMINO-ACID: glutamate residue
MUTATION-TO-AMINO-ACID: lysine residue
heme-binding site
COFACTOR-BOUND: heme{FE+2}
FOR-BINDING-OF: O2
References
- Clinical Diagnosis & Management by Laboratory Methods,
J.B. Henry (ed), W.B. Saunders Co., Philadelphia,
PA. 1991, pg 653
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998