Anemia
Dr Bharat Agarwal
Consultant Pediatric Hematologist and Oncologist, B.J.Wadia Hospital for Children, Mumbai, India
First Created: 02/26/2001 

Introduction

Anemia is defined as a reduction in the oxygen-carrying capacity of the 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 the 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 the 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 the reticuloendothelial system, where the flow of blood is slow, particularly in the splenic pulp. A child is said to be anemic when the hemoglobin and/or hematocrit is two standard deviations below the 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

AGE Hb (gm%)RBC (m/L)HCT%MCV (cu.mm)MCH (pg)MCHC%Retic%
1 day 18.0 5.14 6111936.031.632
4 weeks14.24.04310635.533.50.6
1 year11.64.6357725.033.00.9
10-12 years13.04.8398027.033.01.0
Adult- Men16.05.4478729.034.01.0
Adult- women14.04.8428729.034.01.0

The lower limit of hemoglobin at the 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 the age of 3 months needing no treatment and the same will represent severe anemia needing blood transfusion in the newborn period.

Classification and Aetiology Of Anaemia

There are four basic causes of anemia - loss, destruction, sequestration, and hypoproduction.

Anemia can be further classified by:
RBC size - micro, normal, and macrocytic anemia.

RBC shape - e.g. Sickle cell.

Etiology

Etiological Classification of Anemia

TABLE 2: ETIOLOGICAL CLASSIFICATION OF ANAEMIA

Blood loss:
  • Acute
  • Chronic
Decreased iron assimilation:
  • Nutritional deficiency
  • Hypoplastic or aplastic anemia
  • Bone marrow infiltration like leukemia & 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:


 case of hypochromic-microcytic anemia

Macrocytic anemia:

The causes include-

Non-megaloblastic anemia

  • Hemolytic anemia
  • Liver disorder, obstructive jaundice
  • Post splenectomy
  • Bone marrow disorders like hypoplastic anemia, dyserythropoietic anemia, myelofibrosis etc.
  • Alcoholism
  • COPD

Megaloblastic anemia

  • Folate deficiency
  • B12 deficiency
  • Congenital disorders of DNA synthesis like Orotic aciduria, etc.


Macrocytic anemia

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:


approach to normocytic normochromic anemia


Anemia Anemia 02/26/2001
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