Though Pneumocystis carinii has common epitopes with fungi (Lundgren et al. 1992b) and may be considered a fungus rather than a protozoan (Stringer et al. 1989), its diagnosis and treatment are more like that of protozoa, justifying inclusion among parasites in clinical practice. Pneumocystis carinii pneumonia (PCP) was the first opportunistic infection recognized in AIDS patients, American (Gottlieb et al. 1981) as well as European (Gerstoft et al. 1982). HIV positive individuals with decreasing CD4+ (T-helper lymphocyte) counts not taking any chemoprophylactic are at high risk of PCP.
The symptoms often start insidiously with tiredness, fever, dyspnoea, and dry cough. The incubation time may be several months, more often a few weeks. Severe chest pain, resolving spontaneously, may precede an episode of PCP (Bygbjerg, unpublished). Ambulant presentation with almost no clinical signs and even with a normal chest X-ray is common; however, the dyspnoea may suddenly worsen, and the chest X-ray's appearance turn into that of 'white lungs' (Figure 27.1). Lung stethoscopy is often unhelpful, for example, normal, but increased respiration rates, 30-40 per minute in severe cases, and clinically visible hypoxaemia (cyanosis) should alert the clinician to hospitalize and further examine the patient immediately, since manifest respiratory insufficiency, requiring mechanical ventilation may supervene, if diagnosis and treatment are delayed. In case of super- or co-infection with fungi or bacteria, the patient's dry cough may become productive; otherwise the characteristic glass-glossy/ foamy sputum can only be induced by hypertonic saline inhalation or
brought up by bronchoalveolar lavage (BAL) (see below). The outcome of PCP in Scandinavian patients with AIDS is about 15% mortality, which may rise to 44% if mechanical ventilation is required (Lidman et al. 1989; Pedersen et al. 1989).
Extrapulmonary P. carinii have been described from most internal organs post mortem as well as in vivo (Cohen and Stoeckler 1991), including lymph nodes, spleen, liver, bone marrow, bones, adrenal glands, gastrointestinal tract, kidneys, thyroid gland, heart, pleura, pancreas, peritoneum, eyes, ears, and brain (Garcia and Bruckner 1993). Patients taking prophylaxis with aerosolized pentamidin, attaining only the lungs, rather than taking systemic prophylaxis with sulfamethoxazole-trimethoprim (co-trimoxazole), are at particular risk of extrapulmonary infection (Witt et al. 1991).
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