MECHANISM OF ANEMIA

BLOOD LOSS
● Acute bleeding, e.g. from wounds, surgical, ectopic pregnancy, placenta praevia
● Chronic blood loss, e.g. hookworm infection, schistosomiasis, gastrointestinal bleeding, menorrhagia

DECREASED RED CELL PRODUCTION
● Lack of essential nutrients, e.g. deficiencies of iron,
folate, vitamin B12, protein
● Depressed bone marrow activity, e.g. anaemias associated with chronic disease such as tuberculosis, HIV disease, chronic nephritis, chronic hepatitis,
connective tissue disorders, malignant disease, leukaemias
● Due to drugs, chemicals, ionizing radiation, some viruses
● Thalassaemia syndromes

INCREASED RED CELL DESTRUCTION
(HAEMOLYSIS)
● Inherited haemolytic anaemias:
– Haemoglobinopathies, e.g. sickle cell diseases,
thalassaemia syndromes
– Red cell enzyme deficiencies, e.g. G6PD
deficiency, pyruvate kinase deficiency
– Red cell membrane defects e.g. hereditary
spherocytosis
● Non-immune acquired haemolytic anaemias:
– Infections, e.g. malaria, African trypanosomiasis, meningococcal septicaemia, C. perfringens
infection, bartonellosis
– Pre-eclampsia and HELLP syndrome (haemolysis, elevated liver enzymes, low platelet count)
– Conditions which cause disseminated intravascular coagulation (DIC)
– Haemolytic uraemic syndrome
– Hypersplenism and splenomegaly, e.g. visceral
leishmaniasis, hyper-reactive malaria, splenomegaly, myelofibrosis
– Burns
– Venomous snake and spider bites
– Chemicals, oxidant drugs, local herbal remedies
– Paroxysmal nocturnal haemoglobinuria
● Immune acquired haemolytic anaemias (DAT positive):
– Haemolytic disease of the newborn
– Haemolytic blood transfusion reaction
– Warm reactive autoantibody, e.g. drug-induced chronic lymphatic leukaemia, lymphoma, systemic lupus erythematosus
– Cold reactive autoantibody, e.g. M. pneumonia infection, lymphoma
– Paroxysmal cold haemoglobinuria