Page 476 - Medicine and Surgery

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472 Chapter 12: Haematology and clinical immunology

blocking antibodies (bind to intrinsic factor and pre- deficiency is associated with neural tube defects in
vents binding to B 12 )orbinding antibodies (bind to the fetus.
the IF:B 12 complex preventing absorption). Antifolate drugs include methotrexate, trimetho-
Atrophic gastritis is present with plasma cell and lym- prim, anticonvulsants and alcohol.
phoid infiltration affecting the fundus and body of the
stomach. There is achlorydia and absent secretion of in-
Clinical features
trinsic factor.
Symptoms and signs of anaemia (see page 467). Patients
may also complain of a sore mouth and tongue (glossi-
Clinical features
tis).
Theonsetofperniciousanaemiaisusuallyinsidiouswith
worseningsymptomsofanaemia(seepage467).Patients
Investigations
may also have neurological complications of vitamin B 12
Redcell folate level are low. In many cases the cause is
deficiency (see page 471).
not obvious and further investigations may have to be
undertaken including barium follow through or upper
Investigations
gastrointestinal endoscopy and biopsy.
Full blood count will demonstrate a macrocytic anaemia
(raised MCV). Vitamin B 12 is low. The Schilling test is
used to differentiate the causes of vitamin B 12 deficiency Management
(see Table 12.4). The underlying cause should be identified and treated
where possible. Prior to treatment with oral folic acid
Management supplements, concurrent vitamin B 12 deficiency must be
Parenteral vitamin B 12 replacement is required for life. identified and treated to avoid the neurological compli-
Clinical improvement can be seen in 48 hours and a cations of B 12 deficiency. Prophylaxis is advised in preg-
reticulocytosis can be demonstrated 2–3 days after com- nancy, haemolytic anaemias, premature babies, dialysis
mencing therapy. patients and those taking methotrexate.

Folate deficiency Haemolytic anaemia
Definition
Definition
Deficiency of folate causes a megaloblastic anaemia due
Haemolytic anaemia is defined as an anaemia resulting
to abnormal DNA synthesis.
from increased breakdown of red cells and shortened red
blood cell life span (normal 120 days).
Aetiology/pathophysiology
Folic acid is the precursor to the folates, which are in-
volved in the synthesis of DNA (see Fig. 12.4). Causes of Aetiology
The causes of haemolytic anaemia are shown in Table
folic acid deficiency:
12.5.
Low intake is most common in elderly, people living

in poor social conditions and chronic alcoholics. Folic
acid is found in fresh vegetables and meat, but may Pathophysiology
be destoyed by overcooking. Shortening of the life span of red cells does not always
Malapsorption occurs due to small bowel disease (es- cause anaemia. If the increased loss can be compen-

pecially if affecting the jejunum) such as coeliac dis- sated for by an up-regulation of the bone marrow (which
ease. can increase output between six and eight times) then a
Increased requirements occur in haemolytic con- compensated haemolytic state will arise. In addition to

ditions, myeloproliferative disorders, other rapidly bone marrow up-regulation, reticulocytes (red cell pre-
growing tumours and severe inflammatory disease. cursors) may be released prematurely. Haemolysis can
In pregnancy there are increased requirements and be divided into two categories: