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Chapter 12: Myelodysplastic and myeloproliferative disorders 481

The Duffy red cell antigen is necessary for invasion and blood cultures. If there are signs of neurological in-

by P. vivax.Many Africans do not express this antigen volvement a CT scan of the head should be performed
and have a relative resistance. but should not delay treatment.
The sickle cell gene reduces mortality in P. falciparum

infections.
Management
α thalassaemia increases susceptibility to P. vivax re-

If causative species is not known, or if the infection is
ducing subsequent P. falciparum infection.
mixed, initial treatment should be as for P. falciparum.
β thalassaemia reduces parasite multiplication due to

P. falciparum is treated by oral quinine, mefloquine,
the persistence of fetal haemoglobin which is resistant
Malarone (proguanil and atovaquone), or Riamet
to digestion by malaria.
(artemether with lumefantrine). If the patient is un-
Symptoms are associated with the asexual stages. In the
able to swallow, is vomiting or has impaired con-
gametocyte stage there is genetic recombination causing
sciousness intravenous quinine is used. Falciparum
antigenic variation.
malaria can progess rapidly in unprotected individu-
als. Treatment should be considered in patients with
Clinical features
features of severe malaria even if the initial blood
Most patients have a history of recent travel to an en-
tests are negative. Other supportive treatments in-
demicarea.Patientsdevelopsymptomsincludingcough,
clude monitoring for, and correction of hypogly-
fatigue, malaise, spiking fever and rigors, arthralgia and
caemia, blood transfusion for severe anaemia. In se-
myalgia. The classical description of paroxysmal chills
vere cases intensive care may be required.
and shivering followed by a spike of high temperature
Benign malaria (P. vivax P.ovale or P. malariae)is
is only seen in the minority of patients. Other symp-
treated with chloroquine although some P. vivax is
toms include anorexia, nausea, vomiting, diarrhoea and
developing resistance. P. malariae and ovale require
headache. Examination may reveal tachycardia, pyrexia,
subsequent treatment with primaquine to eradicate
hypotension, pallor and in chronic cases splenomegaly.
latent parasites in the liver (after exclusion of G6PD
There should be a high index of suspicion for malaria in
deficiency).
any patient presenting with symptoms following travel
Chemoprophylaxis is dependent on the area that is
to endemic areas.
to be visited and specialist advice should be sought.
In general where there is no chloroquine resistance
Complications
weeklychloroquineisused.Inareasofchloroquinere-
P. falciparum is potentially life threatening due to cere-
sistance a combination of chloroquine and proguanil
bral malaria (progressive headache, neck stiffness, con-
may be used. Alternative regimes include mefloquine,
vulsions and coma), severe anaemia (red cell lysis and re-
Maloprim (dapsone and pyrimethamine) or doxycy-
duced erythropoesis), hypoglycaemia, hepatic and renal
cline. Prophylaxis should begin prior to entering an
failure. It may also lead to severe intravascular haemol-
endemic area (in order to detect establish tolerance)
ysis causing dark brown/black urine (blackwater fever)
and should continue for 4 weeks after leaving the en-
particularly after treatment with quinine.
demic areas. Mosquito repellent nets and sprays, and
protective clothing should also be used.
Investigations
Diagnosis is by identification of parasites on thick and
thin blood films. Although the first specimen is positive
in 95% of cases at least three negative samples are re- Myelodysplastic and
quired to exclude the diagnosis. The thick film is more myeloproliferative disorders
sensitive for diagnosis and the thin film is used to dif-
ferentiate the parasites and quantify the percentage of Myelodysplastic syndromes
parasite infected cells. Other diagnostic tests include
ELISA antigen detection and polymerase chain reaction Definition
(PCR) tests. Other investigations should include a full Myelodysplastic syndrome (MDS) is a pre-malignant
blood count, U&E, liver function tests, clotting, urine condition in which there are abnormal stem cells