Pneumocystis jiroveci

An opportunistic fungus that normally doesn't grow in healthy people, P jiroveci colonizes immunocompromised people. Affects many people with HIV.

 

Epidemiology

Seasonal periodicity

 

Formerlly known as PCP.

Grows as a budding yeast with a capsule that prevents phagocytosis.

Classification and Characteristics

 

Virulence Factors

 

Transmission and Infection

Rarely person-to-person.

Many people believe we are infected during childhood, making most people latent carriers. The fungus thus would become active during times of immunocompromise. However, this theory is not fully proven.

 

 

Clinical Manifesations

Variable manifestations.

Fever, nonproductive cough, and dyspnea.

Grows in lung, but can spread to lung or brain.

Can form solitary pulmonary nodule that can mimic lung cancer; also can spread around body, especially to the brain and meninges, where it can cause meningitis.

Can also spread to bone and cause osteolytic myelitis.

 

 

Diagnosis

This pathogen is impossible to culture.

Cytology and tissue biopsy are required. Cysts are round/oval 5-7 um. Grooves or folds, with central dots, are present.

Chest X ray classically shows diffuse interstitial infiltrate, starting in the perihilum and most often bilateral. However, CXR may also be normal. Pleural effusions very rare.

 

Intra-alveolar foamy exudate with small bubbles present

interstitial inflammation

GMS silver stain can be used for fungus.

 

Lab studies often show

 

Treatment

Maintain SaO2 above 90%.

Antibiotic options include:

Corticosteroids can be used as adjuvant therapy, especially with low O2 sats.

TMP-SMX prophylaxis can be used for people with CD4 counts <200 x106/L