HEMOGLOBINOPATHIES

Thalassemias

Sickle Cell Anemia

Different forms of hemoglobin:

• Hemoglobin A
  • Formed of two "alpha" and two "beta" subunits
  • Most common form in most adults
• Hemoglobin A2
  • Formed of two "alpha" and two "delta" subunits
• Hemoglobin F
  • Formed of two "alpha" and two "gamma" subunits
• Hemoglobin C
  Abnormal hemoglobin formed from mutated (single base-pair substitution) beta chain(s) and normal alpha chains
  Found in primarily in Africa
  Homozygosity (HbCC) produces mild chronic hemolytic anemia and splenomegaly. No sickling occurs but aplastic crises do; risk for gallstones is increased
• Hemoglobin E
  • Abnormal hemoglobin formed from mutated (single base-pair substitution) beta chain(s) and normal alpha chains
  • Found primarily in South East Asia
  • Heterozygosity ("Hb E trait") causes mild microcytosis but no clinical problems
  • Homozygosity (HbEE) causes more significant microcytosis but again, no clinical problems--if this is noted on newborn screening, should repeat for confirmation and after 2mos of age (to r/o HbE-Beta-Thalassemia--see below)
  • Heterozygosity for Hb E plus heterozygosity for Beta-Thalassemia ("Hemoglobin-E Beta-Thalassemia") causes severe, transfusion-dependent, hemolytic anemia
• Hemoglobin "Bart's"
  • An abnormal hemoglobin formed of four "gamma" subunits, seen in some Thalassemias