Pneumocystis carinii is a very common organism that may be residing harmlessly in the lungs of healthy persons. IT is only when the body’s defenses are lowered due to cancer, cancer treatment or aids that it may cause pneumonia. It is often the first indication that a person with human immunodeficiency virus (HIV) infection has developed the disease.
In many people, a fever, shortness of breath and a dry cough may develop. These symptoms generally manifest after several weeks. The capacity of the lungs to optimally oxygenate the blood may be hampered leading to shortness of breath.
Pneumocystis carinii, is now actually considered a fungus rather than a protozoan and causes disease only when bodily defenses are weakened especially when there are deficiencies in cell-mediated immunity as in hematologic malignancies, cancer chemotherapy, lymphoproliferative diseases and AIDS. Approximately 30% of the patients with HIV infection have P. carinii pneumonia as the initial aids confirming diagnosis and more than 80% of AIDS patients develop this infection at some point of time if prophylaxis is not given.
X-rays reveal either no abnormality or just a patchy infection, similar to what is observed in some viral infections. The diagnosis is arrived at by microscopic examination of a sputum sample obtained by either of the two techniques—sputum induction (where a vapor is used to stimulate coughing) or bronchoscopy (in this an instrument is inserted into the airways to collect a sample.
To prevent pneumocystis pneumonia in people at risk, the combination antibiotic trimethoprim-sulfamethoxazole can be administered. The side effects of this drug, particularly common in people having AIDS, are rashes, fever and a reduced number of infection fighting white blood cells. Other preventive drug treatments include atovaquone, dapsone and pentamidine ( which is inhaled directly into the lungs like an aerosol.)
A person infected with pneumocystis pneumonia, will have cough, fever, trouble breathing (especially after exercise) and experience chest tightness. If symptoms such as these are observed, it is best to see a doctor right away. In most cases, the infection is mild but severe pneumocystis pneumonia may be fatal if it is not treated promptly. Pneumocystis pneumonia can be diagnosed by sending fluid or tissue from the lungs to the lab for testing.
The disease is rare in people with healthy immune systems but common among those suffering from AIDS. Pneumocystis pneumonia could develop in patients who are on immune suppressant medications (people having undergone organ transplant surgeries) and in those who have undergone bone marrow transplantation.
In seriously ill children, symptoms of pneumocystis pneumonia begin quite suddenly with a cough, fever and breathing difficulty. It is the most common pediatric ailment related to AIDS, especially in infants younger than 6 months, and its prevention constitutes a very important aspect of AIDS care. Sick and weak infants could also develop pneumocystis pneumonia. The infant could be between 3 to 6 months old and without any fever, but gradually begins to breathe quick, fast breaths. As the lung infection deteriorates, the breathing becomes more difficult and its chest muscles begin to retract (pull in unnaturally) with each breath. The child’s fingernails, lips and skin could take on a bluish or grayish tinge.
Pneumonia carinii is an opportunistic organism as it causes disease only under favorable conditions. When a person is immunocompromised, Pneumonia carinii proliferates and cause infection. The mechanisms involved in the growth of the organism within the alveoli are not yet understood fully. As the organism replicates, it gradually fills the alveoli. As the pneumonia progresses, fluid is accumulated and the scarring of the tissue occurs. This lowers the respiratory function and reduces the levels of oxygen in the bloodstream.
However, in individuals whose immunity is compromised due to underlying diseases like cancer, HIV/AIDS, solid organ and/or bone marrow transplantation and in individuals receiving chronic corticosteroids or other medications that affect the immune system, Pneumocystis carinii may result in infecting the lungs.
Individuals in advanced stage of AIDS have sparked a particular interest, since Pneumocystis Pneumonia (PCP) was considered as a rare infection prior to the AIDS epidemic. Up to 70% of individuals in the U.S. suffering from advanced AIDS would develop PCP, much before the use of preventive antibiotics in the treatment of PCP.
PCP in AIDS infected patients, usually develops slowly and is less severe. The symptoms include several weeks of cough, fevers, and progressive shortness of breath, associated with exertion. Patients who do not have AIDS but are suffering from PCP usually get sick faster and become severely ill.
Some patients are categorized as high-risk groups as they are at a higher risk pf contracting PCP. These groups include:
Although the incubation period of Pneumocystis pneumonia is not definitely known, it is believed to be between four and eight weeks.
The major symptoms of the disease are fever, a non productive cough and shortness of breath. Lesser known symptoms include production of sputum, blood in sputum, chest pain and difficulty breathing.
Most patients experience symptoms for a week or two before they consult the physician. The disease occasionally spreads outside of the lungs and infects other organs like the spleen, lymph nodes, bone marrow or liver.
Doctors can diagnose pneumocystis pneumonia either by x-rays or by finding the organism in lab tested samples of lung fluids. The doctor may need to use a bronchoscope to extract a tissue sample from inside the child’s lungs. The sample is then sent to a lab where special chemical stains can identify the pneumocystis organism.
Even if your child has no other medical problems, it is advisable to call the doctor immediately if the child has unusually rapid breathing or has difficulty breathing, is coughing or has a bluish grey tinge to his nails, lips or skin.
The clinical diagnosis is confirmed by the typical appearance of the chest x-ray which reveals widespread pulmonary infiltrates, and an arterial oxygen level drastically lower than would be expected from the symptoms. The diagnosis can be fully confirmed by the pathologic identification of the disease causing organism in induced sputum or bronchial washings which when obtained by bronchoscopy with coloration by toluidine blue or immunofluorescence assay, show characteristic cysts.
Antibiotics are used either singly or in special combinations to treat pneumocystis pneumonia. They may be taken orally or administered intravenously (into the veins) for atleast 2 weeks. The antibiotic treatment will prolong upto 3 weeks if the child suffers from AIDS. The doctor may add a steroid medication depending on the severity of the PCP infection.
In the event that your child has a weakened immune system due to any previous infection, consult your doctor about treating your child with antibiotics to prevent pneumocystis infection as a precautionary measure.
All infants born to HIV positive mothers should be started on PCP prophylaxis at 1 month of age until a confirmed diagnosis is obtained on their HIV status.
The generally prescribed drug is trimethoprim-sulfamethoxazole (TMP-SMX) 20 mg/kg/day (trimethoprim) in four doses IV or po for 21 days. Even if the diagnosis is not confirmed, the commencement of therapy should not be delayed, as cysts may persist for weeks. The main potential side effects, especially in patients suffering from AIDS, are fever, skin rash and neutropenia. Alternative treatments are pentamidine 3 to 4 mg/kg IV once daily, atovaquone 750 mg po bid, trimethoprim 20 mg/kg/day po with dapsone 100 mg/day po, or clindamycin 300 to 450 mg po qid with primaquine base 15 mg/day po. All treatment courses should be followed for 21 days. One of the main limitations of pentamidine is the high incidences of toxic side effects, including hepatotoxicity, renal failure, leucopenia, fever, rash, hypoglycemia, and gastric intolerance. The overall mortality rate of hospitalized patients is 15 to 20%. For those with a PaO2 < 70 mm Hg, adjunctive therapy with corticosteroids is advised. The prescribed regimen is prednisone 40 mg bid (or its equivalent) for the first 5 days, 20 mg bid for the next 5 days, and then 20 mg/day for the duration of treatment. Hypoxemia, the need for intubation and late fibrosis is reduced by corticosteroids. Supportive treatment consists of O2 theraapy, sometimes needing positive end-expiratory pressure to maintain PaO2 >= 60 mm Hg.
It is recommended that AIDS patients who have also suffered from P carinii pneumonia or those who have a CD4 count < 200/mm3 should receive prophylaxis with TMP-SMX 80/400 mg/day; In case this treatment is not well tolerated, aerosolized pentamidine 300 mg monthly or dapsone 100 mg/day po, can be administered. These prophylactic regimens are also often advocated for other vulnerable populations.