Pneumocystis Pneumonia (PCP or PJP)

What is Pneumocystis pneumonia?

Pneumocystis jirovecii is a fungus that lives only in humans. Most people are exposed in early childhood with no illness. A healthy immune system, especially CD4 T cells, keeps it in check. When immunity is weakened, the organism multiplies in the air sacs (alveoli), filling them with foamy material that blocks oxygen transfer.

PCP was one of the first illnesses recognized in the AIDS epidemic in 1981 and remains a common AIDS-defining illness in people who do not know they have HIV. Today, more cases occur in people without HIV who take immune-suppressing treatments, and in that group it tends to start more suddenly and be more severe.

Who is at risk?

• HIV: CD4 count below 200 cells/mm³, or CD4 under 14%, or a history of oral thrush. See HIV/AIDS.
• Organ and stem cell transplant recipients, particularly in the first 6 to 12 months
• Blood cancers such as leukemia and lymphoma, and their treatment
• Long-term corticosteroids: about 20 mg of prednisone or more daily for 4 weeks or longer, especially combined with other immunosuppressants
• Other immune-suppressing drugs: some chemotherapy, rituximab, and drugs for autoimmune disease
• Inherited immunodeficiency and severe malnutrition
• Premature or malnourished infants in low-resource settings

PCP spreads through the air between people, which is why transplant units sometimes see clusters.

Symptoms

• Dry cough that does not bring up much sputum
• Fever, sometimes low-grade
• Shortness of breath, first on exertion, then at rest
• Chest tightness or discomfort
• Fatigue and weight loss
• Fast breathing and low oxygen, often worse than the chest exam suggests

In people with HIV, symptoms usually build slowly over 2 to 4 weeks. In people without HIV, they often develop over a few days and progress to respiratory failure faster.

Diagnosis

• Oxygen levels: pulse oximetry or arterial blood gas. A drop in oxygen saturation with walking is a characteristic early clue.
• Chest X-ray: often shows haziness in both lungs, but can be normal early.
• CT scan: typically shows "ground-glass" changes in both lungs. A normal CT makes PCP unlikely.
• Sputum tests: induced sputum (after breathing salt-water mist) is tested with special stains or PCR.
• Bronchoscopy with lavage: washing fluid from the lungs through a camera tube, the most reliable test.
• Blood tests: a raised beta-D-glucan supports the diagnosis; LDH is often high. CD4 count and HIV testing are done if HIV status is unknown.

Treatment

Antibiotic treatment

• Trimethoprim-sulfamethoxazole (TMP-SMX, co-trimoxazole) is the first choice, given by mouth or intravenously, usually for 21 days.
• For people who cannot take it (for example, sulfa allergy), alternatives include primaquine plus clindamycin, intravenous pentamidine, or atovaquone for mild disease. Primaquine and dapsone require a G6PD test first.

Steroids

People with moderate to severe PCP (low blood oxygen) also receive a tapering course of corticosteroids, started within 72 hours. In HIV, this clearly reduces deaths and the need for a ventilator by calming the inflammation that occurs as the fungus dies.

Supportive care

Oxygen therapy, and in severe cases intensive care and mechanical ventilation.

HIV treatment

People with HIV start antiretroviral therapy, usually within 2 weeks of starting PCP treatment, which restores immunity and prevents relapse.

Complications

• Respiratory failure needing a ventilator
• Pneumothorax (collapsed lung) from damaged lung tissue
• Drug side effects: rash, low blood counts, high potassium, kidney and liver problems
• Death: mortality is roughly 10 to 20% in people with HIV and higher, around 30 to 50%, in people without HIV, especially if a ventilator is needed

Prevention (prophylaxis)

PCP is largely preventable. Doctors recommend preventive TMP-SMX, often one tablet daily or three times a week, for:

• People with HIV and a CD4 count under 200 (or under 14%), until the CD4 count stays above 200 for at least 3 months on HIV treatment
• Transplant recipients for a set period after transplant
• People on high-dose, long-term steroids or certain chemotherapy and immunotherapy regimens

TMP-SMX also protects against toxoplasmosis. Alternatives for people who cannot take it include dapsone, atovaquone and monthly inhaled pentamidine.

Frequently asked questions

What is the difference between PCP and PJP?

They are the same infection. The organism was once called Pneumocystis carinii, giving the abbreviation PCP. It was renamed Pneumocystis jirovecii when scientists found the human form was a different species, so some doctors now use PJP. Many still say PCP, which can now stand for Pneumocystis pneumonia.

Is Pneumocystis pneumonia contagious?

The fungus spreads between people through the air, and most people are exposed in childhood without getting sick. It only causes pneumonia in people with weakened immune systems. For this reason, hospitals may separate patients with PCP from transplant or other immunosuppressed patients.

What are the symptoms of PCP pneumonia?

The main symptoms are a dry cough, fever and gradually worsening shortness of breath, especially on exertion. People often feel tired and lose weight. In people with HIV, symptoms build over weeks. In people on immune-suppressing medicines, they can worsen over just a few days.

What CD4 count is a risk for PCP?

The risk rises sharply when the CD4 count falls below 200 cells/mm³. People with HIV at or below this level, or with CD4 under 14% or a history of oral thrush, should take preventive TMP-SMX until antiretroviral therapy keeps their CD4 count above 200 for at least 3 months.

Can you get Pneumocystis pneumonia without HIV?

Yes. Many cases today occur in people without HIV who have organ or stem cell transplants, blood cancers, or take long-term corticosteroids or other immune-suppressing drugs. In these people, PCP often develops faster and is more severe, so prevention is recommended for those at high risk.