Hematology: Hemoglobinopathies

Hgb F globulin chains

A and gamma

Hgb A2 globulin chains

A and S

Hgb A globulin chains

A and B

How does Hgb F affect oxygen binding

much higher binding affinity

Hgb S globulin chain

B chain

What is SCD

when a patient has a sickle cell gene and B thalassemia gene

Where on the B chain is the sickle cell mutation

position 6, glutamic acid replaced by valine

What does the change in RBC charge in sickle cell do to the RBC

changes how RBC interact (motility)

When do RBCs have the sickle cell RBC shape

when deoxygenated (<85% homo)

Reversible sickle cell

RBCs change shape in response to O2

Irreversible sickle cell

RBCs sickle regardless of O2

What causes the anemia in sickle cell

extravascular hemolysis (chronic)

BM in sickle cell

hyperplastic

Most common symptom of sickle cell in the ER

vaso-occlusive crisis: RBC aggregate in distant vasculature

Why do megaloblastic episodes occur in sickle cell

folate depletion due to attempt of compensation

Retinal ischemia

clotting in small eye capillaries

Avascular necrosis

impaired blood supply to head of femur/ humerus

Sickle cell anemia type

normocytic, normochromic

Retic count in sickle cell

10-25% marked polychromatic

SCD screen

presence of tactics (crystals)

SCD confirmatory test

hgb electrophoresis

What can cause a false positive SCD screen

hyperlipidemia

Alkaline electrophoresis does what

measure hgb A and S

Acidic electrophoresis does what

separates S from D and G

Best method of SCD confirmation

Capillary electrophoresis

What pathogen does SCD protect the patient from

Malaria (P. falciparum)

RBC morphology in Hgb C

crystals (gold bar)

Hgb C B chain change

lysine replaces glucose

What other anemia is needed to be differentiated from Hgb E

IDA

Hgb SC RBC morphology

dark red sharp RBC

Hgb M

methemoglobin (chocolate blood no O2)

Unstable hgb disease RBC morphology

Heinz bodies