Introduction
Pneumocystis pneumonia (PCP) affects humans with compromised immune systems. It is caused by a fungus called pneumocystis jirovecii. Pneumocystis pneumonia was the main cause of death in AIDS patients before the availability of drugs against AIDS. Since pneumocystis pneumonia is a life-threatening disease, it is key to treat it with prophylactic (preventive) measures.
What Is Pneumocystis Jirovecii Fungus?
Pneumocystis jirovecii is common and found in the lungs of healthy individuals without any health issues. Healthy children by the age of two or four years old are found to have antibodies against the fungus. However, the fungus affects individuals with a weak immune response (immunocompromised). The fungus causes pneumocystis pneumonia is them and can cause death.
How Does Pneumocystis Pneumonia Develop?
In an immune-compromised individual, when exposed to the fungus, the trophic form of the pneumocystis jirovecii fungus attaches itself to the alveoli of the lung. Since the immune system is compromised, the fungus multiplies easily and causes pneumocystis pneumonia.
What Are the Symptoms of Pneumocystis Pneumonia?
Symptoms may start to show within weeks or months. The symptoms present as:
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Sudden onset and low-grade fever.
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Non-productive cough (with little or no mucus).
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Progressive chest discomfort.
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On exertion, tachycardia (increased heart rate) and tachypnea (increased breathing rate).
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Breathing difficulty (dyspnea).
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Low oxygen levels in the blood (hypoxemia), characteristic laboratory finding for pneumocystis pneumonia.
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Symptoms of underlying diseases such as that for AIDS.
Who Is at Risk for Pneumocystis Pneumonia?
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Individuals with AIDS or a history of AIDS.
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An individual who had a bone marrow or an organ transplant.
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Individuals with cancer and blood cancer.
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Individuals on prolonged medication, for example, corticosteroids.
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Individuals are receiving chemotherapy for cancer.
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Individuals with pre-existing lung disease.
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Individuals with diseases to connective tissues, such as rheumatoid arthritis.
How to Diagnose Pneumocystis Pneumonia?
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Chest X-Ray - A chest radiograph can reveal diffuse bilateral interstitial infiltrates, lobar infiltrates, solitary or multiple nodules that can progress to cavitary lesions, and pneumothorax (collapsed lung).
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Chest Computed Tomography (CT) - Ground-glass opacities or cystic lesions.
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Identifying the Fungus With Tests-
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Polymerase chain reaction assay of sputum confirms the diagnosis.
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Bronchoalveolar lavage (examination of fluid from the lung).
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Fluorescein antibody (microscopic examination).
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Dye staining with a methenamine silver stain.
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Blood Tests - Low oxygen levels, elevated beta-D-glucan.
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Lung Biopsy.
What Are the prophylactic measures for Pneumocystis Pneumonia?
Prophylaxis aims to prevent the first occurrence of these infections (primary prophylaxis) or their recurrence (secondary prophylaxis). Prophylaxis for individuals is indicated when:
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Individuals have AIDS and CD4+ T-lymphocyte count less than 200 cells/μL (a millionth of a liter).
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Has a history of oropharyngeal candidiasis.
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AIDS-defining diseases, such as herpes simplex, and encephalopathy.
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Persistent CD4+ T-lymphocyte count less than 200 cells/μL.
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Received an organ transplant.
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Hematopoietic stem cell transplant recipient.
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On prolonged corticosteroid medications.
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Individuals receiving immunosuppressive therapy, such as Cyclosporin.
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Individuals with cancer or on cancer treatment.
The duration for prophylaxis may vary for individuals depending on the risk of pneumocystis pneumonia for one. For example, individuals should be on prophylaxis for six months following a transplant, and for those with a history of pneumocystis pneumonia to have lifelong prophylaxis is recommended. Combined antiretroviral therapy (cART) is the gold standard for prophylaxis. Studies found that introducing highly active antiretroviral treatment (HAART) decreased the incidence of pneumocystis pneumonia by 94 %. Trimethoprim-Sulfamethoxazole is the most commonly used drug for pneumocystis pneumonia prophylaxis. Other drugs include Dapsone, Pentamidine, Atovaquone, and Pyrimethamine in combination.
Primary Prophylaxis Regimen - Primary prophylaxis is recommended for individuals having AIDS with CD4+ T-lymphocyte count less than 200 cells/μL or a history of oropharyngeal candidiasis.
- Trimethoprim or Sulfamethoxazole - Given orally- one double-strength or one single-strength tablet daily is the first choice of drug. An alternate choice would be one double-strength tablet three times a week. The side effects (rashes on the skin, dark stool, or urine) are usually seen within the month of treatment. A majority of individuals are seen as tolerant of drugs.
- Pentamidine Aerosol Prophylaxis - 300 milligrams of Pentamidine with a nebulizer (respirgard II) monthly. Indicated when the individual cannot tolerate the oral administration of Trimethoprim or Sulfamethoxazole. Nebulizer is given by a professional (doctor or nurse) every month. Side effects include cough and bronchospasm, which are treated with the inhalation of a bronchodilator. With aerosol inhalation, the upper lobe of the lung may not get adequate drugs, and infection of the same has been observed.
- Dapsone - Given orally- 50 milligrams twice daily or 100 mg once daily. Dapsone was shown to be as effective as Trimethoprim or Sulfamethoxazole.
- Atovaquone - Given orally- single dose of 1500 mg daily or in two doses of 750 mg daily. It is another alternative prophylactic drug usually given with high-fat meals (red meat) for maximum absorption.
Secondary Prophylaxis - Secondary prophylaxis is recommended lifelong for individuals who have had a history of pneumocystis pneumonia or at least until immunity is regained as a response to antiretroviral therapy (ART).
- Trimethoprim or Sulfamethoxazole - Given orally, one double-strength or one single-strength tablet daily is the first choice of drug. An alternate choice would be one double-strength tablet three times a week.
- Dapsone - Given orally, 50 mg twice daily or 100 mg once daily.
- Dapsone Plus Pyrimethamine Plus Leucovorin - Low dose given orally, 50 mg plus 50 mg plus 25 mg weekly.
- Dapsone Plus Pyrimethamine Plus Leucovorin - High dose given orally, 200 mg plus 75 mg plus 25 mg weekly.
- Pentamidine Aerosol Prophylaxis - 300mg of Pentamidine with a nebulizer (Respirgard II) monthly.
- Atovaquone - 1500 mg once a day with food daily.
- Atovaquone Plus Pyrimethamine Plus Leucovorin - 1500 mg plus 25 mg plus 10 mg with food daily.
Prophylactic medicines result in toxicity to the liver and kidney on prolonged use and hence should be weighed against the benefits before the treatment regimen begins. Primary and secondary prophylaxis can be discontinued in patients who have responded to highly active antiretroviral treatment (HAART) and with an increase of CD4+ count to more than 200 cells/μL for at least three months. Secondary prophylaxis is restarted when the CD4+ count drops below 200 cells/μL.
Conclusion
The risk of developing infections increases dramatically with progressive immune system impairment. An increasing number of pneumocystis pneumonia cases are seen in individuals prone to the condition. There is no vaccine to prevent pneumocystis pneumonia. With the life-threatening nature of the disease, a prophylactic measure can save lives.
