Pneumocystis jirovecii pneumonia

pneumonia resulting from infection with pneumocystis jirovecii.

Introduction

Pneumocystis jirovecii pneumonia (PCP) is a serious infection caused by the fungal organism Pneumocystis jirovecii. Formerly known as Pneumocystis carinii pneumonia, this condition primarily affects individuals with weakened immune systems, such as those with HIV/AIDS, undergoing chemotherapy, or receiving immunosuppressive therapy.

Etiology

Pneumocystis jirovecii is the organism responsible for PCP. It is considered a fungus based on molecular analysis, although it shares characteristics with protozoa.

Epidemiology

PCP is a global disease and a common opportunistic infection among immunocompromised patients, particularly among individuals with HIV/AIDS before widespread use of antiretroviral therapy (ART).

Pathophysiology

The organism attaches to the alveolar lining of the lungs and leads to inflammation and characteristic foamy exudates within the alveoli, hindering normal oxygen exchange.

Clinical Presentation

Symptoms of PCP include:

• Progressive shortness of breath
• Nonproductive cough
• Fever
• Weight loss
• Night sweats

Diagnosis

Diagnosis of PCP can be challenging and typically involves a combination of clinical presentation, imaging, and laboratory analysis, including:

• Chest X-ray and high-resolution CT scan showing diffuse bilateral infiltrates
• Identification of Pneumocystis organisms in respiratory specimens via microscopy or molecular techniques
• Blood tests showing elevated lactate dehydrogenase (LDH) levels

Treatment

Treatment for PCP typically includes antibiotics such as trimethoprim-sulfamethoxazole (TMP-SMX). For patients with sulfa allergies, alternative medications include Pentamidine, Atovaquone, or the combination of Clindamycin and Primaquine.

Prophylaxis

Prophylactic measures are recommended for high-risk individuals, such as those with low CD4 counts due to HIV/AIDS. TMP-SMX is commonly used for prevention.

Outcomes

With appropriate treatment, the prognosis for PCP can be good, particularly for those without HIV/AIDS. However, the condition can be life-threatening for those with severe immunosuppression.

See Also

• Opportunistic infection
• Immunocompromised host
• HIV/AIDS
• Respiratory infection
• Fungal infection

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