Page 479 - Medicine and Surgery

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Chapter 12: Haemoglobin disorders and anaemia 475

Complications syndrome or cerebral infarction require exchange blood
Patients have a susceptibility to infections including transfusionstoremovesicklecells.Transfusionsmayalso
streptococcal infections and osteomyelitis often due be indicated in patients with regular severe crises and
to salmonella. Avascular necrosis particularly of the preoperatively.
femoral head may occur. Patients may develop renal fail-
ureduetorecurrentrenaldamageandpapillarynecrosis. Prognosis
Retinal detachment and proliferative retinopathy may Thereismarkedvariationintheseverityofthecondition,
result in blindness. See also complications of haemolytic some patients have a relatively normal life span with few
anaemia (page 473). complications. In the most severe cases patients die from
severe infarctions or sequestration.
Investigations
Full blood count shows anaemia. Blood film shows a α-Thalassaemia

high reticulocyte count and sickle shaped red blood
cells. Definition
Sickle screening tests use a reducing solution, which
Inherited haemoglobinopathy with defective synthesis
causes HbS to precipitate. They are used as a first line of the α-globulin genes. It is mainly found in the Far
test and for screening preoperatively. East, Middle East and Africa.
Haemoglobinelectrophoresisisusedtodiagnoseboth

sickle cell trait and sickle cell disease (see Fig. 12.5). Aetiology
X-ray of the tubular bones may show destruction and
α-Thalassaemia is caused by gene deletions. There are
medullary sclerosis together with periosteal bone for- four copies of the α gene, two on each chromosome 16.
mation. Deletion may be of one or both α chain genes on each
of the chromosomes.

Management
Clinical features
Treatment is largely symptomatic with prophylactic an-
Deletion of all four copies of the α gene (–/–) prevents
tibiotics,folicacidandpneumococcalvaccination.Man-
production of any viable haemoglobin. This disorder
agement of a painful crisis includes oxygenation, ade-
is also termed haemoglobin Bart’s (γ 4 )hydrops syn-
quate hydration and analgesia. Any associated bacterial
drome and results in a stillbirth or neonatal death.
infection should be treated with antibiotics. Acute se-
Deletion of three genes (–/α-) causes HbH disease (a
questration requires blood transfusion, as patients be-
moderate anaemia with splenomegaly and the pro-
comeshocked.Severecrisessuchaspriapism,acutechest
duction of HbH (β 4 )fromthe excess β chains). Treat-
ment is not usually required.
Deletion of one (-α/αα)ortwo genes (-α/-α or –/αα)
Origin HbA 2 HbS HbF HbA causes α-thalassaemia trait in which there are micro-
cytic red blood cells with or without a mild anaemia.
Normal
Investigations
Full blood count shows microcytosis with or without
Sickle Trait anaemia. The diagnosis may be confirmed by quantita-
tive globin chain synthesis.

Sickle Disease β-Thalassaemia
Definition
Figure 12.5 Haemoglobin electrophoresis in sickle cell anae- Inherited haemoglobinopathy with defective synthesis
mia. of the β-globulin chain.