Anaemia (Anemia) : Definition, Causes, Classification, Symptoms, & Treatment

Anaemia, Anemia : Etiology, Types, Morphology, Signs, Symptoms, Diagnosis, Management, & Prevention


  • Anemia (Anaemia) is defined as a reduction in the oxygen-transporting capacity of blood, which usually stems from a decrease in the red cell mass to subnormal levels.
  • For clinical detection of anemia, Haemoglobin concentration in blood is considered as parameter.
  • Lower extreme of Normal haemoglobin concentrations for detection of anemia
    – for Males : 13 gm/dl
    – for Females : 11.5 gm/dl
    – for New born infants : 15 gm/dl (at birth) & 9.5 gm/dl (at 3 months)


Causes :

  • Blood loss (hemorrhage)
  • Increased red cell destruction (hemolysis)
  • Decreased red cell production

Subnormal level of haemoglobin causes lowered oxygen carrying capacity of the blood.
Lowered oxygen carrying capacity of the blood, in turn, initiates compensatory physiologic adaptations such as follows:

  • increased release of oxygen from haemoglobin;
  • increased blood flow to the tissues;
  • maintenance of the blood volume; and
  • redistribution of blood flow to maintain the cerebral blood supply.

Eventually, however, tissue hypoxia develops causing impaired functions of the affected tissues. The degree of functional impairment of individual tissues is variable depending upon their oxygen requirements. Tissues with high oxygen requirement such as the heart, CNS and the skeletal muscle during exercise, bear the brunt of clinical effects of anaemia.


  • Microcytic (iron deficiency, thalassemia)
  • Macrocytic (folate or vitamin B12 deficiency)
  • Normocytic but with abnormal shapes (hereditary spherocytosis, sickle cell disease)

Clinical Features

In symptomatic cases of anaemia, the presenting features are:


  • Shortness of breath
  • Organ failure
  • Shock


  • Pallor, fatigue, lassitude
  • With hemolysis: jaundice and gallstones
  • With ineffective erythropoiesis: iron overload, heart and endocrine failure
  • If severe and congenital: growth retardation, bone deformities due to reactive marrow hyperplasia

General menifestations are:

  • Pallor (It is the most common and characteristic sign which may be seen in the mucous membranes, conjunctivae and skin.)
  • Tiredness, Easy fatiguability, Generalised muscular weakness, Lethargy
  • Headache, attacks of faintness, giddiness, tinnitus, drowsiness, numbness and tingling sensations of the hands and feet.
  • Retinal haemorrhages may occur if there is associated vascular disease or bleeding diathesis.
  • Menstrual disturbances such as amenorrhoea and menorrhagia and loss of libido.
  • Mild proteinuria and impaired concentrating capacity of the kidney may occur in severe anaemia.
  • Anorexia, flatulence, nausea, constipation and weight loss may occur.
  • A hyperdynamic circulation may be present with tachycardia, collapsing pulse, cardiomegaly, midsystolic flow murmur, dyspnoea on exertion, and in the case of elderly, congestive heart failure.
  • In older patients, there may be symptoms of cardiac failure, angina pectoris, intermittent claudication, confusion and visual disturbances.

In addition to the general features, specific signs may be associated with particular types of anaemia.

Investigation of Anemic subject

Anemic subject is examined as follows:

  • Review of full medical history
  • After obtaining the full medical history pertaining to different general and specific signs and symptoms, the patient is examined for evidence of anaemia.
  • Special emphasis is placed on colour of the skin, conjunctivae, sclerae and nails. Changes in the retina, atrophy of the papillae of the tongue, rectal examination for evidence of bleeding, and presence of hepatomegaly, splenomegaly, lymphadenopathy and bony tenderness are looked for.
  • In order to confirm or deny the presence of anaemia, its type and its cause, the following plan of investigations is generally followed, of which complete blood counts (CBC) with reticulocyte count is the basic test.

Haemoglobin estimation
Peripheral blood film examination
Red cell indices
Leucocyte & platelet count
Reticulocyte count
Bone marrow examination



1. Haemorrhagic anemia (Anemia due to Blood loss)

  • Acute anemia
    e.g. Trauma
  • Chronic anemia
    e.g. GIT lesions, Gynecologic disturbance

2. Hemolytic anemia (Anemia due to Increased RBC destruction)

(a). Intrinsic (Intracorpuscular) RBC Abnormalities

  • Inherited / Hereditary
    Red cell membrane abnormality Red cell enzyme deficiency Haemoglobin synthesis disorders
    Membrane skeletal proteins, e.g. Hereditary spherocytosis, Hereditary elliptocytosis Glycolytic pathway, e.g. Pyruvate Kinase Deficient globin synthesis, e.g. Thalassaemias
    Membrane lipids, e.g. Abetalipoproteinemia Hexose monophosphate shunt, e.g. G6PD Abnormal globin synthesis (Haemoglobinopathies), e.g. sickle cell disease
    Pyrimidine 5´ nucleotidase
  • Acquired
    Abnormal membrane
    Paroxysmal nocturnal haemoglobinuria

(b). Extrinsic (Extracorpuscular) RBC Abnormalities

  • Immune

    Warm antibodies Cold antibodies
    •Autoimmune, e.g. SLE, RA
    •Drugs, e.g. L-dopa, methyldopa, mefenamic acid, penicillin, quinidine, fludarabine
    •Lymphoid malignancy, e.g. CLL, myeloma, lymphoma
    •Other malignancy, e.g. lung, colon, kidney, ovary, thymoma
    •Others, e.g. ulcerative colitis, HIV
    •Infection, e.g. mycoplasma, EBV, syphilis
    •Lymphoproliferative disorders, e.g. lymphoma


    Red cell antigen induced
    Transfusion reaction
    Haemolytic disease of the newborn
  • Non-immune
    Mechanical Infection Chemical/physical
    Prosthetic valves Intracellular organisms, e.g. Malaria Oxidative drugs, e.g. dapsone, maloprim
    Microangiopathic, e.g. DIC, HUS, TTP Toxins, e.g. C. Perfringens Copper (Wilson’s disease)
    March haemoglobinuria Burns

3. Anemia due to Impaired RBC production

(a). Disturbed proliferation and differentiation of stem cells

  • Aplastic anemia
  • Pure red cell aplasia

(b). Disturbed proliferation and maturation of erythroblasts

  • e.g.
    Defective DNA synthesis Defective hemoglobin synthesis
    Deficiency or impaired utilization of vitamin B12 and folic acid, e.g. megaloblastic anemias Deficient heme synthesis, e.g. iron deficiency, sideroblastic anemias
    Anemia of renal failure, e.g. erythropoietin deficiency Deficient globin synthesis, e.g. thalassemias
    Anemia of chronic disease, e.g. iron sequestration, relative erythropoietin deficiency
    Anemia of endocrine disorders

(c). Marrow replacement

  • Primary hematopoietic neoplasms, e.g. acute leukemia, myelodysplastic syndromes

(d). Marrow infiltration (myelophthisic anemia)

  • Metastatic neoplasms
  • Granulomatous disease


Management depends on type of anemia.

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