Anemia is defined as reduction in the oxygen carrying capacity of blood, as observed by reduced levels of hemoglobin concentration and red cell mass (Hematocrit) leading to tissue hypoxia. It reflects the disturbance of the dynamic balance between production and destruction of erythrocytes and hemoglobin. In normal subjects, the average life span of red cell i.e. time between the release of red cell from bone marrow and its disappearance from circulation, is between 100 to 120 days. The cells destroyed each day are replaced by new cells released from marrow, with the result the red cell population in the blood consists of cells ranging in the age from one to 120 days. Thus, approximately 1% or slightly less of body's red cells are destroyed and replaced each day. Any disruption of this balance - such as reduced production or increased destruction leads to anemia. The aged cells are removed from circulation by the reticuloendothelial cells, principally in the walls of sinusoids of reticuloendothelial system, where the flow of blood is slow, particularly in the splenic pulp. Child is said to be anemic when the hemoglobin and / or hematocrit is two standard deviation below mean for that particular age and sex.
The following table gives the normal values (normal mean and lower limit of normal) of various hematological parameters at different age groups (Table 1)
Table 1: AVERAGE NORMAL BLOOD VALUES AT DIFFERENT AGE GROUPS
||Hb (gm%)||RBC (m/L)||HCT %||MCV (cu.mm)||MCH (pg)||MCHC %||Retic %|
Lower limit of hemoglobin at newborn period is 16 gm%, at 3 months- 9 gm%, 6 months to 6 years- 10 gm%, 7 to 12 years -12 gm%. Thus, 9 gm% - 11 gm% Hb is normal for a child around age of 3 months needing no treatment and same will represent severe anemia needing blood transfusion in newborn period.
CLASSIFICATION AND AETIOLOGY OF ANAEMIAThere are four basic causes of anemia - loss, destruction, sequestration and hypoproduction.
Anemia can be further classified by:
RBC size - micro, normo, and macrocytic anemia.
RBC shape - e.g. Sickle cell.
Etiological Classification of Anemia:TABLE 2: ETIOLOGICAL CLASSIFICATION OF ANAEMIA
|Decreased iron assimilation:|
- Nutritional deficiency
- Hypoplastic or aplastic anemia
Bone marrow infiltration
& other malignancies, myelodysplastic syndrome
- Dyserythropoietic anemia
|Increased Physiologic requirement:|
Extracorpuscular like alloimmune & isoimmune hemolytic anemia, microangiopathic anemias, infections, hypersplenism,
- Intracorpsular defect like:
- Red cell membranopathy i.e. congenital spherocytosis, elliptocytosis
- Hemoglobinopathy like HbS, C, D, E, etc. Thalessemia syndrome
- RBC enzymopathies like G6PD deficiency, PK deficiency, etc.
MORPHOLOGICAL CLASSIFICATION OF ANEMIA IN CHILDREN
Microcytic hypochromic anemia:
The causes include:
- Iron deficiency anemia
- Abnormal hemoglobinopathies and Thalassemia syndrome
- Anemia of chronic infection and inflammations
- Sideroblastic anemias
- Lead poisoning
Following algorithm shows the approach to such a case of hypochromic-microcytic anemia:
The causes include-
- Hemolytic anemia
- Liver disorder, obstructive jaundice
- Post splenectomy
- Bone marrow disorders like hypoplastic anemia, dyserythropoietic anemia, myelofibrosis etc.
- Folate deficiency
- B12 deficiency
- Congenital disorders of DNA synthesis like Orotic aciduria, etc.
Normocytic, Normochromic anemia
The causes include :
- Post-hemorrhage - early stage
- Hemolytic anemia
- IDA - early stage
- Systemic diseases like endocrinal, renal and hepatic diseases
- Bone marrow disorders like hypoplastic anemia, myeloinfiltration, dyserythropoiesis, myelodysplasia and masked megaloblastosis.
The following algorithm shows an approach to normocytic normochromic anemia: