Hemoglobin

• Hemoglobin A (nl 96%): 2 α, 2 β chains
• Hemoglobin F (nl <1%): 2 α, 2 γ chains, Increased O2 affinity
• Hemoglobin A2 (nl 1-3%): 2 α, 2 δ chains

Hemoglobinopathies

Hgb C

• α2, β2 with lysine substituted @ position 6 in β chain

• Moderate hemolytic anemia if homozygous

• Splenomegaly common

• Increased # target cells

Hb SC

• Pt has genes for both Hgb S and C

• Fewer, less painful vasoocclusive crises than SS

• Splenomegaly later than SS

• Increased sludging due to incr Hgb (not anemic!)

• More frequent bony infarcts

• Retinal vascular changes may occur

Hgb S β-thal

• More severe than either alone

• Moderately severe hemolytic anemia (microcytic)

• Serious vaso-occlusive crises

• % Hgb S varies (60-90%) depending on type of β-thal trait

Hemoglobin E: beta-chain variant (alpha2 / beta2, 26Glu->Lys); prevalent in populations from Southeast Asia, particularly Thailand and Cambodia