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72 / Chapter 5 Macrocytic anaemias

Differential d iagnosis of m acrocytic
Table 5.10 Causes of macrocytosis other

than megaloblastic anaemia. a naemias

The clinical history and physical examination
Alcohol may suggest B 12 or folate defi ciency as the
Liver disease cause. Diet, drugs, alcohol intake, family history,
history suggestive of malabsorption, presence
Myxoedema
of autoimmune diseases or other associations
Myelodysplastic syndromes with pernicious anaemia (Table 5.4 ), previous
Cytotoxic drugs gastrointestinal disease or operations are all impor-

tant. The presence of jaundice, glossitis or a
Aplastic anaemia
neuropathy are also valuable indications of mega-
Pregnancy loblastic anaemia.

The laboratory features of particular importance
Smoking
are the shape of macrocytes (oval in megaloblastic
Reticulocytosis anaemia), the presence of hypersegmented neu-
Myeloma and paraproteinaemia trophils and of leucopenia and thrombocytopenia
in megaloblastic anaemia and the bone marrow
Neonatal
appearance. Assay of serum B 12 and folate is essen-
than mature red cells and so haemolytic anaemia is tial. Exclusion of alcoholism (particularly if the
an important cause of macrocytic anaemia. Th e patient is not anaemic), liver and thyroid function
other underlying conditions listed in Table 5.10 are tests, and bone marrow examination for myelodys-
usually easily diagnosed provided that they are con- plasia, aplasia or myeloma are important in the
sidered and the appropriate investigations to exclude investigation of macrocytosis not caused by B 12 or
B 12 or folate defi ciency are carried out. folate defi ciency.

SUMMARY size of circulating red cells (MCV > 98 fl ). ■ Other gastrointestinal diseases as well as a

stomach which facilitates B 12 absorption by
■ Macrocytic anaemias show an increased

the ileum.

Causes include vitamin B 12 (B 12 , cobalamin)
vegan diet may cause B 12 defi ciency.
or folate defi ciency, alcohol, liver disease,

■ Folate defi ciency may be caused by a poor
hypothyroidism, myelodysplasia,
paraproteinaemia, cytotoxic drugs, aplastic
diet, malabsorption (e.g. gluten - induced
anaemia, pregnancy and the neonatal
period.
pregnancy, haemolytic anaemias,

malignancy).
■ B 12 or folate defi ciency cause enteropathy) or excess cell turnover (e.g.

megaloblastic anaemia, in which the bone ■ Treatment of B 12 defi ciency is usually with

marrow erythroblasts have a typical injections of hydroxocobalamin and of
abnormal appearance. folate defi ciency with oral folic

■ B 12 defi ciency is usually caused by B 12 (pteroylglutamic) acid.

malabsorption brought about by pernicious ■ Rare causes of megaloblastic anaemia
anaemia in which there is autoimmune include inborn errors of B 12 or folate
gastritis, resulting in severe defi ciency of transport or metabolism, and defects of
intrinsic factor, a glycoprotein made in the DNA synthesis not related to B 12 or folate.

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