2. Anaemia
Anaemia is defined as reduced haemoglobin concentration
in blood below the lower limit of the normal range for the
age and sex of the individual. In adults, the lower extreme
of the normal haemoglobin is taken as 13.0 g/dl for males
and 11.5 g/dl for females. Newborn infants have higher
haemoglobin level and, therefore, 15 g/dl is taken as the
lower limit at birth.
In pregnancy, there is haemodilution and, therefore, the
lower limit in normal pregnant women is less (10.5 g/dl)
than in the non-pregnant state.
3. Pathophysiologic Classifications of
Anaemia
I. Anaemia due to blood loss This is further of 2 types:
A. Acute post-haemorrhagic anaemia
B. Anaemia of chronic blood loss
II. Anaemia due to impaired red cell formation A disturbance due to
impaired red cell production from various causes may produce anaemia.
These are as under: …
4. Pathophysiologic Classifications of
Anaemia(b)
A.Cytoplasmic maturation defects
1. Deficient haem synthesis: iron deficiency anaemia
2. Deficient globin synthesis: thalassaemic syndromes
B. Nuclear maturation defects Vitamin B12 and/or folic acid deficiency:
megaloblastic anaemia
C. Haematopoietic stem cell proliferation and differentiation
abnormality e.g.
1. Aplastic anaemia
2. Pure red cell aplasia
5. Pathophysiologic Classifications of
Anaemia(c)
D. Bone marrow failure due to systemic diseases (anaemia of chronic
disorders) e.g.
1. Anaemia of inflammation/infections, disseminated malignancy
2. Anaemia in renal disease
3. Anaemia due to endocrine and nutritional deficiencies
(hypometabolic states)
4. Anaemia in liver disease.
6. Pathophysiologic Classifications of
Anaemia(d)
E. Bone marrow infiltration e.g.
1. Leukaemias
2. Lymphomas
3. Myelosclerosis
4. Multiple myeloma
F. Congenital anaemia e.g.
1. Sideroblastic anaemia
2. Congenital dyserythropoietic anaemia.
7. Pathophysiologic Classifications of
Anaemia(e)
III. Anaemia due to increased red cell destruction (haemolytic anaemias)
This is further divided into 2 groups:
A. Intracorpuscular defect (hereditary and acquired).
B. Extracorpuscular defect (acquired haemolytic anaemias).
8. Morphologic Classifications of
Anaemia
1. Microcytic, hypochromic MCV, MCH, MCHC are all reduced
e.g. in iron deficiency anaemia and in certain noniron
deficient anaemias (sideroblastic anaemia, thalassaemia,
anaemia of chronic disorders).
2. Normocytic, normochromic MCV, MCH, MCHC are all normal
e.g. after acute blood loss, haemolytic anaemias, bone
marrow failure, anaemia of chronic disorders.
9. Morphologic Classifications of
Anaemia(b)
3. Macrocytic MCV is raised e.g. in megaloblastic anaemia due
to deficiency of vitamin B12 or folic acid. With these general
comments on anaemias, a discussion of the specific types of
anaemias is given in the following pages.
