Megaloblastic Anaemia – B. Pharma 2nd Semester Pathophysiology notes pdf

Megaloblastic Anaemia



of megaloblastic anemia

Epidemiology of megaloblastic anemia

of megaloblastic anemia


At the
end of the PDF Notes, the students will be able to

       Define  megaloblastic anemia

       Discuss  the etiology of megaloblastic anemia

       Describe  the epidemiology of megaloblastic anemia

       Explain the pathogenesis of
megaloblastic anemia

Megaloblastic Anaemia

       It is caused by impaired DNA synthesis and others by folate and
vitamin B12 deficiency

       Abnormality in the haematopoietic precursors in the bone marrow –
maturation of the nucleus is delayed relative to that of the cytoplasm.

       Formation of morphologically abnormal nucleated
red cell precursor called megaloblast in the bone marrow

       Anaemia described is hyperchromic macrocytic

Etiological Classification of 

Megaloblastic Anaemia


A. Inadequate dietary intake e.g. strict
vegetarians, breast-fed infants.

B. Malabsorption

1. Gastric causes: pernicious anaemia,
gastrectomy, congenital lack of intrinsic factor.

2. Intestinal causes: tropical sprue, ileal
resection, Crohn’s disease, intestinal blind loop syndrome, fish-tapeworm


A.      Inadequate dietary intake e.g. in
alcoholics, teenagers, infants, old age, poverty.

B. Malabsorption e.g. in tropical sprue, coeliac disease, partial gastrectomy,
jejunal resection, Crohn’s disease.

C. Excess demand

       1. Physiological: pregnancy, lactation, infancy.

       2. Pathological: malignancy, increased haematopoiesis, chronic
exfoliative skin disorders, tuberculosis, and rheumatoid arthritis.

D. Excess urinary folate loss e.g. in active liver disease, congestive heart failure

Pathophysiology of 

Megaloblastic Anaemia

       The common feature in megaloblastosis is a defect in DNA synthesis
in rapidly dividing cells.

        RNA and protein synthesis are

        Unbalanced cell growth and
impaired cell division occur since nuclear maturation is arrested.

        More mature RBC precursors
are destroyed in the bone marrow prior to entering the blood stream
(intramedullary hemolysis)

Vitamin B12

       Vitamin B12 or cobalamin is a complex organometallic compound having
a cobalt atom situated within a corrin ring.

       The liver is the principal storage site
of vitamin B12

       Major source of loss is via bile and shedding of intestinal
epithelial cells.

        A major part of the excreted
vitamin B12 is reabsorbed in the ileum by the IF resulting in enterohepatic

Sources of Vitamin

      Micro-organisms (Soil, water animal intestine)


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