Page 322 - Textbook of Pathology, 6th Edition

306 malabsorption, excess folate utilisation such as in pregnancy 4. Others. In addition to the cardinal features mentioned
and in various disease states, chronic alcoholism, and excess above, patients may have various other symptoms. These
urinary folate loss. Folate deficiency arises more rapidly than include: mild jaundice, angular stomatitis, purpura, melanin
vitamin B deficiency since the body’s stores of folate are pigmentation, symptoms of malabsorption, weight loss and
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relatively low which can last for up to 4 months only. anorexia.
Patients with tropical sprue are often deficient in both
vitamin B and folate. Combined deficiency of vitamin B 12 Laboratory Findings
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and folate may occur from severe deficiency of vitamin B 12 The investigations of a suspected case of megaloblastic
because of the biochemical interrelationship with folate anaemia are aimed at 2 aspects:
metabolism. A. General laboratory investigations of anaemia which include
3. OTHER CAUSES. In addition to deficiency of vitamin blood picture, red cell indices, bone marrow findings, and
B and folate, megaloblastic anaemias may occasionally be biochemical tests.
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induced by other factors unrelated to vitamin deficiency. B. Special tests to establish the cause of megaloblastic anaemia
These include many drugs which interfere with DNA as to know whether it is due to deficiency of vitamin B 12
synthesis, acquired defects of haematopoietic stem cells, and or folate.
rarely, congenital enzyme deficiencies. Based on these principles, the following scheme of
investigations is followed:
Clinical Features
A. General Laboratory Findings
Deficiency of vitamin B and folate may cause following
SECTION II
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clinical manifestations which may be present singly or in 1. BLOOD PICTURE AND RED CELL INDICES. Esti-
combination and in varying severity: mation of haemoglobin, examination of a blood film and
1. Anaemia. Macrocytic megaloblastic anaemia is the evaluation of absolute values are essential preliminary
cardinal feature of deficiency of vitamin B and/or folate. investigations (Fig. 12.19):
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The onset of anaemia is usually insidious and gradually i) Haemoglobin. Haemoglobin estimation reveals values
progressive. below the normal range. The fall in haemoglobin
2. Glossitis. Typically, the patient has a smooth, beefy, red concentration may be of a variable degree.
tongue. ii) Red cells. Red blood cell morphology in a blood film
3. Neurologic manifestations. Vitamin B deficiency, parti- shows the characteristic macrocytosis. However,
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cularly in patients of pernicious anaemia, is associated with macrocytosis can also be seen in several other disorders
significant neurological manifestations in the form of such as: haemolysis, liver disease, chronic alcoholism,
subacute combined, degeneration of the spinal cord and hypothyroidism, aplastic anaemia, myeloproliferative
peripheral neuropathy (Chapter 30), while folate deficiency disorders and reticulocytosis. In addition, the blood smear
may occasionally develop neuropathy only. The underlying demonstrates marked anisocytosis, poikilocytosis and
pathologic process consists of demyelination of the peripheral presence of macroovalocytes. Basophilic stippling and
nerves, the spinal cord and the cerebrum. Signs and occasional normoblast may also be seen (Fig. 12.20, A).
symptoms include numbness, paraesthesia, weakness, iii) Reticulocyte count. The reticulocyte count is generally
ataxia, poor finger coordination and diminished reflexes. low to normal in untreated cases.

Haematology and Lymphoreticular Tissues

Figure 12.19 General laboratory findings in megaloblastic anaemia.