EMQs in Clinical Medicine.pdf - Peshawar Medical College

62 Haematology and oncology
D
A
J
A 24-year-old woman with anaemia and splenomegaly is referred to
the haematologist. Her direct Coombs’ test is negative. Her blood film
shows the presence of reticulocytes and spherocytes.
Hereditary spherocytosis is a genetic defect in the red cell membrane
structure. Most cases are inherited in an autosomal dominant fashion
but the patient can also present without family history as a result of
spontaneous mutation. Patients may present with jaundice at birth but
can also remain asymptomatic for many years. The direct Coombs’ test is
negative in hereditary spherocytosis. This is an important test because
spherocytes are also commonly found in autoimmune haemolytic
anaemia.
Treatment of choice is splenectomy because the spleen is the site of
spherocyte removal.
A 17-year-old tourist from the West Indies presents with pain in his
abdomen and hands. He is pyrexial and anaemic.
Sickle-cell anaemia results from an amino acid substitution in the gene
coding for the chain of Hb, giving rise to altered Hb known as HbS.
HbS polymerizes when deoxygenated, producing characteristically sickleshaped
cells. This results in both a haemolytic anaemia and occlusion of
small blood vessels.
Several sickle-cell crises are recognized:
(i) Infarctive crises give rise to the painful hand and foot syndrome,
avascular necrosis of the femoral head, splenic infarction and
priapism. A patient with hepatosplenomegaly may be suffering from
a sequestration crisis where sickle cells have been trapped in the
liver and spleen.
(ii) Haemolytic crisis resulting in jaundice may be precipitated by an
infection, drug, etc.
(iii) Aplastic crises may occur secondary to infection (usually by
parvovirus).
Full blood count of a 65-year-old woman taking ibuprofen for her
osteoarthritic knee pain for a number of years shows a microcytic
anaemia.
Iron deficiency anaemia classically causes a microcytosis. The most likely
cause in this case is loss from the gastrointestinal tract as a result of
chronic NSAID use.
Full blood count of a 45-year-old man treated for gastric carcinoma
with total gastrectomy reveals a macrocytic anaemia.
F Intrinsic factor secreted by the stomach is required for vitamin B 12
absorption. The Schilling test can be used to determine whether low
serum vitamin B 12 is the result of malabsorption from the terminal ileum
or lack of intrinsic factor secreted by the stomach.