Thursday, May 8, 2014

Heinz Bodies

Heinz Bodies

Background Information of Heinz Bodies
Heinz bodies (also referred to as "Heinz-Ehrlich bodies") are inclusions within RBCs composed of denatured hemoglobin.

Clinical Significance
Heinz bodies are formed by damage to the hemoglobin component molecules, usually through oxidant damage, or from an inherited mutation (i.e. change of an internal amino acid residue). 
As a result, an electron from the hemoglobin is transferred to an oxygen molecule, which creates a reactive oxygen species (ROS) that can cause severe cell damage leading to premature cell lysis. Damaged cells are cleared by macrophages in the spleen, where the precipitate and damaged membrane are removed, leading to characteristic "bite cells". The denaturing process is irreversible and the continual elimination of damaged cells leads to Heinz body anemia.
There are several pathways leading to the hemoglobin damage.
  • NADPH deficiency can cause a dysfunction in glutathione peroxidase which is an enzyme that converts hydrogen peroxide(ROS) into water.
  • G6PD (glucose-6-phosphate dehydrogenase) deficiency exacerbated by administration of oxidant drugs (e.g., primaquine, dapsone, quinidine) can also result in Heinz bodies. G6PD deficient red cells in combination with high levels of oxidants causes a cross-linking of sulfhydryl groups on globin chains which causes a denaturing and formation of Heinz body precipitates.
  • Chronic liver disease
  • Alpha-thalassemia:  Patients whom have partial or complete defects in alpha globin production, leading to a relative abundance of beta globin chains in the cell. These excess beta globin chains aggregate to form HbH, which has decreased solubility and precipitates in the RBC cytoplasm. This is not direct damage to hemoglobin per se, but rather a perturbation in the quaternary structure of hemoglobin.
  • Hyposplenism/asplenia: damaged or absent spleen cannot remove these damaged cells from circulation.

Cellular Description
Heinz bodies appear as small round inclusions within the red cell body, though they are not visible when stained with Romanowsky dyes. They appear more clearly when supravitally stained (e.g., with new methylene blue or bromocresol green).

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