Pneumocystis Carinii Pneumonia

Because of its association with human immunodeficiency virus (HIV) infection, Pneumocystis carinii pneumonia (PCP), a communicable, opportunistic infection, has increased in incidence since the 1980s. It occurs in the following hosts: premature ar malnourished infants; children with primary immunodeficiency disease; patients receiving immunosuppressive therapy (particularly glucocorticoids) far cancer, organ transplantation, or other disorders; and people with acquired immunodeficiency syndrome (AIDS). The organism remains a leading cause of opportunistic infection and death among AIDS patients in industrialized countries.

Causes

PCP is caused by a fungus. It used to be called pneumocystis carinii, but scientists now call it pneumocystis jiroveci. A healthy immune system can control the fungus. However, PCP causes illness in children and in adults with a weakened immune system.

Pneumocystis almost always affects the lungs, causing a form of pneumonia. People with CD4 cell counts under 200 have the highest risk of developing PCP. People with counts under 300 who have already had another opportunistic infection are also at risk. Most people who get PCP become much weaker, lose a lot of weight, and are likely to get PCP again.

Symptoms and Signs

• Fever
• Cough
• Shortness of breath especially with exertion (activity)
• Rapid breathing
• Sputum induction: for special stains to detect Pneumocystis carinii

Diagnostic tests

Histologic studies can confirm P carinii. In many patients with HIV, initial examination of a first-morning sputum specimen (induced by inhaling an ultrasonically dispersed saline mist) may be sufficient. This technique usually is ineffective in patients without HIV.

In all patients, fiberoptic bronchoscopy remains the most commonly used diagnostic tool to confirm PCP. Invasive procedures, such as transbronchial biopsy and open lung biopsy, are less commonly used.

In addition, a chest X-ray may show slowly progressing, fluffy infiltrates and occasional nodular lesions or a spontaneous pneumothorax. These findings must be differentiated from findings in other types of pneumonia or adult respiratory distress syndrome.

A gallium scan may show increased uptake over the lungs even when the chest X-ray appears relatively normal.

In PCP, arterial blood gas (ABG) studies detect hypoxia and an increased A-a gradient.

Treatment

The drug of choice for all types of PCP is trimethoprim-sulfamethoxazole (TMP-SMZ) administered orally or I.V. Adverse reactions include fever, rash, neutropenia, thrombocytopenia, hepatitis, and hyperkalemia.

Pentamidine may be administered slowly I.V. in a single dose of 4 mg/kg/day; it is as effective as TMP-SMZ but is toxic for almost all recipients. Adverse effects include hypotension, cardiac arrhythmia, hyperglycemia or hypoglycemia, azotemia, electrolyte changes, and neutropenia. Other regimens are also prescribed for patients who don't tolerate either of these medications.

Supportive measures, such as oxygen therapy, mechanical ventilation, adequate nutrition, and fluid balance, are important adjunctive therapies. Oral morphine sulfate solution may reduce respiratory rate and anxiety, enhancing oxygenation.

Prevention

Preventive therapy is recommended for AIDS patients, for individuals on chronic high dose corticosteroids, as well as individuals with previous episodes of PCP.

While the most effective preventive drug is trimethoprim-sulfamethoxazole, other options include dapsone, atovaquone, and pentamidine.

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