Opportunistic infections: Pneumocystis Pneumonia (PCP)

What is PCP?

Pneumocystis pneumonia, or PCP, is an opportunistic infection.   In other sections, we discussed the types of infections that occur in patients with AIDS.  Remember, you don’t actually die because you have AIDS, or a low CD4 count--the opportunistic infection is what causes death or sickness.  Opportunistic infections are infections that hit patients with a weak immune system.  The “bug” that causes the infection has an opportunity to cause sickness, because of the person’s weak immune system.  PCP is the number one opportunistic infection in the United States, and the diagnosis of PCP means you have AIDS.

This type of pneumonia was uncommon before 1981, when it was first noticed in young, healthy gay men and people who injected street drugs.  It was the diagnosis of PCP in these young people that began the hunt for the cause, eventually leading scientists to discover HIV.    

What causes PCP?

PCP in humans is caused by a tiny organism called Pneumocystis jirovecii.  The organism used to be called Pneumocystis carinii, until scientists decided to give that name to PCP that affects rats, mice, squirrels, and beavers!  The organism that causes PCP is classified as a fungus and is similar to a protozoa.   Fungus, a primitive organism, is both good and bad and is responsible for yummy portobello mushrooms, yeast to make bread, mold to make penicillin (and ruin your bread), mildew in your shower, and organisms that make you sick.  Fungus is made up of one to many cells and lives in the soil or on plants, animals, and decaying substances, to get its nutrients.

The PCP organism is everywhere, and you were probably exposed to it in childhood, before you were even 4 years old.  However, because your immune system was healthy, you did not get sick.   Pneumocystis jirovecii is spread by air--breathing in the organism.  When your CD4 is less than 200, your immune system is so weak that you have a good chance of getting PCP.  You may have just breathed in a new PCP organism, or you have the organism inside you--yes, it has been hanging around inside you all those years!--and it has become active again, due to your weakened immune system.   

PCP is very common in people with AIDS (a CD4 count less than 200).  In the 1980’s, before it was common to use the antibiotic TMP-SMX (Bactrim) to prevent PCP, the infection occurred in 70-80% of people with AIDS.  Now, it’s uncommon to see PCP unless the person doesn’t know he/she has AIDS, or is not taking the prevention antibiotic.  

This infection, which usually infects the lungs, is not to be taken lightly.  At the least, it will knock you off your feet for weeks to months.  At the most, it is capable of killing you, or can be so serious that you end up in the intensive care unit on a ventilator,  a device that forces oxygen into your lungs when you can’t breathe on your own.  The death rate from this disease can run between 20-40%.  

It is extremely common for a person to be diagnosed with PCP before he/she knows of their HIV diagnosis!  I wish I had a nickel, for all the times I heard a patient tell me that they found out they had AIDS at the same time they found out they had PCP.  This is sad, because that means that many years have likely gone by when the person did not know of their HIV diagnosis and they could have taken medicine to prevent their CD4 from declining to less than 200.   Not only does the person find out they have PCP, but they also find out at the same time, that they are HIV positive, and, they have AIDS!    

What are the symptoms of PCP?

The symptoms of PCP are:

• Slow onset of fever.   In other words, you won’t go from a normal temperature around 98.6F one day to 103 the next day--rather your temperature will increase gradually over days to weeks.
• Slow onset of dry cough.  Note, you can be bringing up phlegm or sputum if you have a bacterial infection on top of PCP.   Your cough can be made worse by taking a deep breath.  
• Slow onset of shortness of breath with exercise, or exerting yourself.  
• Fatigue, or tiredness
• Chest pain, chills, and night sweats may be present but are not as common.

The symptoms of PCP will not come on you like a Mack truck.  Rather, the changes will come on very slowly, almost unnoticed at first, then gradually worsen over a period of days, to weeks, and even months.  

How is PCP diagnosed?

When the person with PCP seeks medical help, he/she will be found to have a fever, a fast heart rate, a fast breathing rate, and a dry (or sometimes wet) cough.  A device called a pulse oximeter will be placed on one of the person’s fingers (or earlobe), and it will measure how saturated the blood is with oxygen.  This amount of oxygen might be normal--95 to 100; however, if the person is asked to exercise, the oxygen rate may decrease quite rapidly.   

The person’s lungs will be examined with a stethoscope; however, the lung exam might be completely normal or the medical provider may hear some abnormal “crinkly”  or “crackly” sounds when the person takes a deep breath.  Some people say that the sound is like the sound you hear if  you rub some strands of your hair between two fingers right next to your ear.  If the lung exam is normal, that does not mean the person does not have PCP.  One could be quite ill and have a normal lung exam.  

There is no laboratory blood test to accurately diagnose PCP.  An arterial blood gas (ABG) test may be done, if the oxygen saturation level is lower than normal.  This test is a bit uncomfortable as it involves sticking a small needle directly into the artery in your  wrist area (right over where you can feel your pulse).  As uncomfortable as the test is, it is very helpful in deciding whether or not a person with suspected PCP is sick enough to need to go into the hospital.  Also, the results are used to decide whether or not the person needs to be on steroid drugs in addition to antibiotics.  

A chest x-ray will be done.  Quite often, in beginning or with mild PCP, the chest x-ray will be normal.  Sometimes, however, the x-ray will show some haziness that some describe as appearing as “ground glass”.  The haziness will usually be in both lungs.  The chest x-ray may often show other more serious abnormalities.  Around 13% of the time, the person will have PCP and another infection at the same time, like tuberculosis, Kaposi’s sarcoma, or bacterial pneumonia.  

One can also do a blood test to measure the lactate dehydrogenase (LDH) level.  Pneumocystic pneumonia will cause the LDH level to be higher than the normal level.  Lactate dehydrogenase is released into the bloodstream when cells or tissues are damaged or destroyed.  The benefit of this test is limited, however, because other illnesses can also cause a high LDH.  The test can be helpful as above normal levels can suggest that a diagnosis of PCP is correct.   Also, after a diagnosis of PCP, the test can be used to see if the lungs are responding to treatment.  

The nurse or lab person may have the sick person cough up some sputum or phlegm into a specimen cup.  Most of these sputum samples are useless, however, as most of the time, the sample comes not from the lungs, but from the throat areas.  There is a test called the “immunofluorescent monoclonal antibody test,” or DFA, that may find pneumocystis jirovecii in sputum.  

The only way to truly diagnose PCP is to go into the lungs with a bronchoscope and take a sample of lung tissue or cells and examine these cells under a microscope.  This procedure is called a bronchoalveolar lavage (BAL), and seeing the little thin-walled cysts, called pneumatoceles, under a microscope, is considered to be proof that one has PCP.  

Cysts of Pneumocystis jiroveci in Smear from Bronchoalveolar Lavage

faculty.ccbcmd.edu

Most of the time, in the HIV clinic, the medical provider will treat the patient without proof that the patient actually has PCP.  The provider may have a strong suspicion, based on his/her past experience working with HIV patients, that this is PCP and doesn’t need any proof in order to treat the patient.   This is good, because treatment for this life-threatening illness won’t be delayed.  

How is PCP treated?

PCP must be treated for a full three weeks.  The first choice drug to treat PCP is TMP-SMX, more commonly known as Bactrim.  The dose is based on weight and a common dose may involve taking 2 tablets three times a day, for a total of 6 pills a day for 21 days.   Patients with more severe PCP, which is measured by the arterial blood gas (ABG) measurement, as mentioned earlier, may need to take oral steroids for the full 21 days, in addition to the Bactrim.  The steroids start at a high dose, then are tapered down over the 21 days.  

Bactrim is famous for causing allergic reactions.  A red rash, itching, and fever are common.  However, because Bactrim is such a good drug for PCP, some medical providers may try to treat you through the rash and fever, or may try you with a smaller dose that you gradually increase.  If your reaction is severe, however, you will need to take a different drug.  The following list contains the alternatives to Bactrim for treating PCP.

1. Pentamidine--directly into the vein (intravenous or IV)
2. Clindamycin + Primaquine
3. Dapsone + Trimethoprim (TMP)
4. Atovaquone 

Is there any way to prevent PCP?

Once you have had PCP, you will need to take Bactrim, or another medicine to prevent PCP, for life.  However, if you are placed on HIV medicine, your CD4 count may go above 200 and you will no longer need to prevent PCP.  If your CD4 count goes above 200 and remains there for 3 months, your medical provider may stop the PCP prevention treatment.  The following list gives the alternative medicines for preventing PCP.  Any person with HIV and a diagnosis of AIDS (either because of an opportunistic infection or because of a CD4 count less than 200) or a CD4 percentage less than 14%, or a diagnosis of oral thrush, should be taking a medicine to prevent PCP.

1. Dapsone (must first get a G6PD test before taking this drug).
2. Atovaquone liquid--very expensive and taste is not that great.
3. Pentamidine--must be breathed into the lungs with a nebulizer machine once a month.