Page 510 - Medicine and Surgery

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506 Chapter 12: Haematology and clinical immunology

Pneumocystis pneumonia (PCP) Investigations
Chest X-ray: The typical features are diffuse bilat-

Definition
eral ground glass infiltrates progressing to widespread
Pneumocystis jirovecii (previously known as Pneumocys-
consolidation in severe cases (sparing of the
tis carinii) causes pneumonia and disseminated illness
costophrenic angles and apices).
in imunocompromised patients. Bronchoalveolar lavage reveals trophozoites & cysts
on silver stain or immunofluorescence.
Aetiology/pathophysiology
Pneumocystis jirovecii is described as a fungus however
it was originally thought to be a protozoan due to its ex- Management
Intravenoushighdoseco-trimoxazole(3weekregimen).
istence as cysts, sporozoites and trophozoites. The reser-
In significant hypoxia steroids are used, patients may re-
voir for infection is thought to be animals, with aerosol
quireCPAPormechanicalventilation.PatientswithHIV
spread. Clinical pneumonia is thought to be a reactiva-
require prophylaxis with co-trimoxazole or monthly
tion of latent infection. The risk of pneumonia increases
nebulised pentamidine if they have a CD4 count of less
as the CD4 count falls, it is rare until the count drops 9
3
below 200 cells/mm . than 0.2 × 10 /L, an AIDS defining illness or following
an previous episode of PCP.
Clinical features
Gradualonsetofnon-specificsymptomsofanorexiaand Prognosis
fatigue followed by dyspnoea, non-productive cough, 90% of patients with a first episode respond to treat-
low-grade fever and tachypnoea. On auscultation there ment and survive. Failure to respond or development of
may be fine crackles or breath sounds may be normal. respiratory failure has significant mortality.