haemoglobin 6: haemolytic anaemia

Question 1

what is haemolytic anaemia?

Answer 1

anaemia as a result of shortened survival of red cells in the circulation

Question 2

how can haemolysis be classified?

Answer 2

inherited/acquired or intravascular/extravascular

Question 3

what are the mechanisms for inherited haemolysis?

Answer 3

abnormalities in cell membrane, haemoglobin or enzymes in red cell

Question 4

what are the mechanisms for acquired haemolysis?

Answer 4

usually extrinsic factors eg microorganisms, chemicals or drugs NB extrinsic factors can interact with red cells with intrinsic abnormalities

Question 5

what is the mechanism for intravascular haemolysis?

Answer 5

very acute damage to red cell

Question 6

what is the mechanism for extravascular haemolysis?

Answer 6

defective red cells are removed by spleen

Question 7

when would you suspect haemolytic anaemia?

Answer 7

• otherwise unexplained normochromic anaemia
• evidence of morphologically abnormal red cells
• evidence of increased haemolysis
• evidence of increased bone marrow activity

Question 8

what are some examples of inherited haemolytic anaemia conditions?

Answer 8

• hereditary spherocytosis (membrane)
• sickle cell anaemia (haemoglobin)
• G6P dehydrogenase deficiency (pentose shunt)
• pyruvate kinase deficiency (glycolytic pathway)

Question 9

what are some examples of acquired haemolytic anaemia conditions?

Answer 9

• autoimmune haemolytic anaemia (membrane)
• microangiopathic haemolytic anaemia (whole red cell - mechanical)
• malaria (whole red cell - microbiological)

Question 10

what is hereditary spherocytosis?

Answer 10

haemolytic anaemia / chronic compensated haemolysis resulting from an inherited intrinsic defect of the red cell membrane - after entering the circulation the cells lose membrane in the spleen and so become spherocytic (extravascular spherocytosis)

Question 11

what are the signs of hereditary spherocytosis?

Answer 11

polychromasia & reticulocytosis (as a result of increased output of red cells by bone marrow), increased bilirubin production -> jaundice & gallstones

Question 12

what is the treatment for hereditary spherocytosis?

Answer 12

splenotomy is the only effective treatment, good diet c/ folic acid tablets to prevent folic acid deficiency

Question 13

why does G6PD deficiency cause haemolysis?

Answer 13

G6PD protects red cell from oxidant damage (oxidants may be generated in the blood eg during infection or exogenous eg broad beans, naphthalene or drugs) - on exposure to oxidant severe intravascular hameolysis occurs & haemoglobin is denatured and forms Heinz bodies

Question 14

where is the gene for G6PD?

Answer 14

X chromosome (therefore males more likely to be affected)

Question 15

what is the mechanism for autoimmune haemolytic anaemia?

Answer 15

production of antibodies directed at red cell antigens - the immunoglobulin bound to the red cell membrane is recognised by splenic macrophages -> remove parts of membrane -> spherocytosis

Question 16

what is the treatment for autoimmune haemolytic anaemia?

Answer 16

use of corticosteroids & other immunosuppressive agents, splenectomy in severe cases

Question 17

what is the treatment for microangiopathic haemolytic anaemia?

Answer 17

removing the cause eg treating severe hypertension / stopping causative drug, plasma exchange if caused by antibody in plasma that leads to fibrin deposition