Anemia and Polycythemia

Question 1

Anemia

Answer 1

Anemia is defined as the deficiency of hb in the blood, either due to decreased red blood cell count or low hb content in the cells.

o2 carrying capacity of blood is reduced

• rbc less than 4 million/mm3
• hb less than 12 gm/dl
• pcv / hematocrit - less than 45%

Mild anemia - hb 8-12
Moderate - 5-8
severe less than 5

heart fails when hb less than 2

Question 2

Classification.

Answer 2

Morphological
Hypochromic Microcytic
- mcv, mch, mchc all low
- occurs due to a defect in red cell formation in which hemoglobin synthesis is impaired to a great extent
- eg - iron deficiency anemia
- thalassemia

normochromic Normocytic
- all normal
occurs in the following conditions:
• substantial blood loss (blood loss anemia)
• hemolysis (hemolytic anemia)
• impairment of red cell production by bone marrow failure or chronic renal failure

normochromic Macrocytic

• mcv above limit
• megaloblasts are seen in bm
• howell jolly body, hyperpigmentation of neutrophils and basophilic stippling seen
• megaloblastic anemia - b12

etiological classification
blood loss anemia
- acute haemorrhage or chronic haemorrhage
• acute haemorrhage depends on the extent of blood loss and the time that has lapsed since bleeding
- usually there is reduction in total blood volume, therefore hb is normal.
- however when the compensatory mechanisms set in to expand the blood volume, hemodilution decreases the hb content.
- therefore, estimation of hb after few hours of acute blood loss does not assess the actual degree of anemia.
• chronic haemorrhage: a person frequently cannot absorb enough iron from the intestines to form hb as rapidly as it is lost. red cells that are much smaller than normal and have too little hb inside them are then produced giving rise to Microcytic, hypochromic anemia.

Aplastic anemia

• anemia due to bone marrow aplasia ie lack of functioning bone marrow.
• eg a person exposed to high dose radiation or chemotherapy for cancer treatment can damage the stem cells of bone marrow, followed in a few weeks by anemia.
• high doses of certain toxic chemicals like insecticides or benzene in gasoline may cause the same effect.
• autoimmune diseases like lupus erythematosus, the immune system begins attacking healthy cells such as bone marrow stem cells
• about half of aplastic anemia cases - cause js unknown, a condition called idiopathic aplastic anemia.
• people with severe aplastic anemia usually die unless treated with blood transfusion or bone marrow transplantation.

nutritional deficiency anemia
• iron deficiency
- most common type of anemia
- usually occurs due to deficiency of iron in the diet
- iron is a vital element in the body because of its requirement in the synthesis of haemoglobin and iron dependent enzymes. when iron is deficient in the body, erythropoiesis is reduced and iron deficiency anemia develops.
- rbc is Microcytic with a low hb content
- easy fatigability
- in children impaired growth as well as poor scholastic development and performance.
- on examination patients will have pallor, but in severe iron deficiency spoon shaped nails (koilonychia)
- a glossy tongue may also develop
- treatment- administration of dietary iron. if a more rapid repletion of body iron is required iron can be administered intramuscularly or intravenously.

• folic acid
• vitamin b12
megaloblastic anemia - due to vit b12 deficiency or due to low folic acid levels
• protein and vitamin c

increased red cell destruction / hemolytic anemia

• hereditary or acquired
• diff abnormalities of the rbc many of which are hereditarily acquired make the cells fragile, so they rupture easily as they go through the spleen.
• even though the no of rbc formed are normal or even much greater than normal, the life span of the fragile red cell is so short that the cells are destroyed faster than they can be formed and serious anemia results.

• in hereditary spherocytosis - red cells are very small and spherical rather than biconcave discs. these cells cannot withstand compression forces due to increased defect of red cell membrane.
- on passing through the splenic pulp and some other tight vascular beds they are easily ruptured by even slight compression.

• sickle cell anemia -

• abnormal haemoglobin s -containing faulty beta chains in the hb molecule.
• when hb is exposed to low conc of o2
• precipitates into long crystals inside the rbc
• crystals elongate the cell and give it the appearance of a sickle
• the precipitated hb also damages the cell membrane making the rbc fragile
• experience a vicious cycle of events - sickle cell disease

erythroblastosis fetalis

• rh positive red blood cells in the fetus are attacked by antibodies from an rh negative mother.
• these antibodies make the rh positive cells fragile leading to rapid rupture and causing the child to be born with serious anemia.

Question 3

rbc/blood indices

Answer 3

mean corpuscular volume (MCV)
- avg volume of rbc expressed in femtoliters
- ratio of the pcv and the rbc count
- MCV (fL) = hematocrit % x 10
rbc count in millions/mm3
normal -
mean corpuscular haemoglobin (MCH)
mean corpuscular haemoglobin concentration (MCHC)

Question 4

polycythaemia

Answer 4

two types

• secondary polycythemia
• whenever the tissues become hypoxic because of too little oxygen in the breathed air such as at high altitudes, or because of failure of oxygen delivery to the tissues such as in cardiac failure the blood forming organs automatically produce large quantities of extra red blood cells.
• red cell count commonly rises to 6-7 million/mm3 about 30% above normal
• a common type of sp - physiological polycythemia occurs in natives who live at altitudes of 14,000-17,000 ft where atmospheric oxygen is very low
• this acts as a compensatory mechanism
• polycythemia vera (erythremia)
• red cell count may be 7-8 million /mm3
• and hematocrit may be 60-70% instead of the normal 40-45%
• caused by a genetic aberration in the hemocytoblastic cells that produce the blood cells.
• they don’t stop producing red cells even when too many cells are present.
• this causes excess production of rbc (and wbc and platelets too)
• hematocrit and total blood volume both inc (on some occasions may even be twice)
• many blood capillaries become plugged with the viscous blood; viscosity of blood in polycythemia inc by about 3 times
• and viscosity of water also increases by 10 times