Page 323 - Textbook of Pathology, 6th Edition

307

Figure 12.20 Megaloblastic anaemia. A, PBF showing prominent macrocytosis of red cells and hypersegmented neutrophils. B, Examination CHAPTER 12
of bone marrow aspirate showing megaloblastic erythropoiesis.

iv) Absolute values. The red cell indices reveal an elevated iii) Other cells. Granulocyte precursors are also affected
MCV (above 120 fl) proportionate to the severity of to some extent. Giant forms of metamyelocytes and band
macrocytosis, elevated MCH (above 50 pg) and normal cells may be present in the marrow. Megakaryocytes are
or reduced MCHC. usually present in normal number but may occasionally
v)Leucocytes. The total white blood cell count may be be decreased and show abnormal morphology such as
reduced. Presence of characteristic hypersegmented hypersegmented nuclei and agranular cytoplasm.
neutrophils (having more than 5 nuclear lobes) in the iv)Marrow iron. Prussian blue staining for iron in the
blood film should raise the suspicion of megaloblastic marrow shows an increase in the number and size of iron
anaemia. An occasional myelocyte may also be seen. granules in the erythroid precursors. Ring sideroblasts are,
vi)Platelets. Platelet count may be moderately reduced however, rare. Iron in the reticulum cells is increased.
in severely anaemic patients. Bizarre forms of platelets v)Chromosomes. Marrow cells may show variety of
may be seen. random chromosomal abnormalities such as chromosome
2. BONE MARROW FINDINGS. The bone marrow breaks, centromere spreading etc. Introduction to Haematopoietic System and Disorders of Erythroid Series
examination is very helpful in the diagnosis of 3.BIOCHEMICAL FINDINGS. In addition to the general
megaloblastic anaemia. Significant findings of marrow blood and marrow investigations and specific tests to
examination are as under (Fig. 12.20,B):
determine the cause of deficiency (described below), the
i) Marrow cellularity. The marrow is hypercellular with following biochemical abnormalities are observed in cases
a decreased myeloid-erythroid ratio. of megaloblastic anaemia:
ii) Erythropoiesis. Erythroid hyperplasia is due to i) There is rise in serum unconjugated bilirubin and LDH as
characteristic megaloblastic erythropoiesis. Megaloblasts a result of ineffective erythropoiesis causing marrow cell
are abnormal, large, nucleated erythroid precursors, breakdown.
having nuclear-cytoplasmic asynchrony i.e. the nuclei are ii) The serum iron and ferritin may be normal or elevated.
less mature than the development of cytoplasm. The nuclei
are large, having fine, reticular and open chromatin that B. Special Tests for Cause of Specific Deficiency
stains lightly, while the haemoglobinisation of the
cytoplasm proceeds normally or at a faster rate i.e. nuclear In evaluating a patient of megaloblastic anaemia, it is
maturation lags behind that of cytoplasm (compared from iron important to determine the specific vitamin deficiency by
deficiency anaemia in which cytoplasmic maturation lags assay of vitamin B and folate. In sophisticated clinical
12
behind, page 299). Megaloblasts with abnormal mitoses laboratories, currently automated multiparametric,
may be seen. Features of ineffective erythropoiesis such random access analysers are employed based on separa-
as presence of degenerated erythroid precursors may be tion techniques by chemiluminescence and enzyme-linked
present. fluorescence detection systems which have largely