• Severe fungal lung infection caused by Pneumocystis jirovecii (formerly Pneumocystis carinii).
• Affects mainly individuals with weakened immune systems.

• People with HIV/AIDS, those who have undergone organ transplants, and individuals on immunosuppression therapy.

• Pneumocystis jirovecii is a unicellular eukaryote with features of both a fungus and a protozoa.

• It is the most common opportunistic infection in AIDS patients and is considered AIDS-defining.

• Can result in severe respiratory symptoms and is potentially fatal.

• Essential for managing PCP in at-risk populations, helping to prevent severe outcomes and complications.

Pneumocystis jirovecii, a fungal organism, is the causative agent of PCP.

Transmission occurs through inhalation of airborne fungal spores.

Immunocompromised individuals (e.g. those with HIV/AIDS or undergoing immunosuppressive therapy) are primarily affected.

The fungus is widespread in the environment but does not cause illness in individuals with healthy immune systems.

• Weakened immune system, particularly in HIV-positive individuals and those on immunosuppressive therapy.

• When the CD4 count drops below 200 cells/mm³.

1. HIV-related factors:
– Oral thrush, persistent fever, or an AIDS-defining diagnosis.
2. Immunosuppressive therapy:
– Use of steroids or other immunosuppressants
3. Haematological malignancies and organ transplants
4. Connective tissue diseases
5. Congenital immune deficiencies such as thymic aplasia, severe combined immune deficiency (SCID), hypogammaglobulinemia

• Targets the lung alveoli, leading to inflammation, compromised gas exchange, lung tissue damage, fluid buildup, and potentially respiratory failure.

• Involves a dysregulated immune response primarily affecting T-cell-mediated immunity, especially in individuals with impaired T-cell function.

Differential diagnoses include:
– Bacterial/Viral pneumonia
– Fungal infections
– Tuberculosis
– Atypical pneumonia
– Pulmonary Kaposi’s sarcoma
– Influenza/Cytomegalovirus infection
– Measles/Varicella pneumonitis
– Coxiella burnetii (Q Fever)
– Thoracic actinomycosis/Nocardiosis
– Lymphocytic interstitial pneumonia
– Pulmonary embolism

• Individuals with weakened immune systems, particularly those with HIV/AIDS
• Transplant recipients
• Individuals with malignancies.

• The incidence of PCP has been significantly reduced due to Highly Active Antiretroviral Therapy (HAART).

• Lower rates due to poor HIV survival, underdiagnosis, and the presence of prior pulmonary infections such as TB.

• Respiratory Symptoms: Progressive dyspnea, non-productive cough, chest discomfort
• Systemic Symptoms: Fever, fatigue, cyanosis, respiratory distress

• Pulmonary: Pneumothorax
• Rare Extrapulmonary Manifestations: Hepatosplenomegaly, lymphadenopathy, choroid lesions

• Respiratory: Exertional dyspnea, tachypnea, chest pain
• Oral Manifestations: Thrush, oral hairy leukoplakia
• Cutaneous: Kaposi’s sarcoma

• Induced sputum
• Bronchoalveolar lavage (BAL)
• Lung biopsy (less common)

• Chest X-ray (CXR): May show bilateral interstitial infiltrates, perihilar fluffy shadows, or pneumothorax
• CT scan: High-resolution CT often reveals ground-glass infiltrates, offering high sensitivity and specificity

• Elevated lactate dehydrogenase (LDH)
• Arterial blood gases (ABG): Show hypoxia and increased alveolar-arterial oxygen tension gradient
• Serum (1→3) beta-D-glucan: Elevated levels are indicative of PCP

• PCR or staining can detect Pneumocystis jirovecii DNA or antigens in sputum or BAL samples

No, it cannot be routinely cultured.

• Mild: Breathlessness on mild exercise; PaO2 >11 kPa; SaO2 >96%; CXR normal or minor perihilar infiltrates
• Moderate: Breathlessness on minimal exercise; PaO2 8-11 kPa; SaO2 91-96%; CXR diffuse interstitial shadowing
• Severe: Breathlessness at rest; PaO2 <8 kPa; SaO2 <91%; CXR extensive interstitial shadowing, possibly with alveolar shadowing

• Modest reduction in vital capacity (VC) and total lung capacity (TLC)
• Consistent decrease in single-breath diffusing capacity for carbon monoxide (DLCO) with high sensitivity

• Co-trimoxazole (trimethoprim-sulfamethoxazole), particularly for mild-to-moderate cases.

• IV pentamidine is used for severe cases.
• Corticosteroids are added if hypoxia is present (PO2 < 9.3 kPa) to reduce the risk of respiratory failure and death.

• Oxygen therapy
• Corticosteroids
• Optimization of antiretroviral therapy (ART) for HIV/AIDS patients.

• 7 days of treatment.

• Atovaquone
• Dapsone with trimethoprim
• Clindamycin with primaquine.

• Due to its lower efficacy, risk of pneumothorax, and relapse.

• Oral co-trimoxazole is recommended for prophylaxis, especially for those with a history of PCP or severe immunosuppression.
• Prophylaxis can be discontinued when CD4 T-cell counts are above 200 cells/mm³ in HIV-positive patients, indicating successful ART.

The prognosis depends on:
– Immune status (e.g., advanced HIV or severe immunosuppression).
– Timeliness of treatment.

Early diagnosis, appropriate treatment, and antiretroviral therapy (ART) significantly improve the prognosis in HIV-related PCP.

With early diagnosis and treatment, the prognosis is generally favourable.

– Overall: 25.4%.
– In ICU-admitted cases: 58%.

PCP can become life-threatening in cases of advanced HIV/AIDS or severe immunosuppression, leading to complications like respiratory failure.

ART has led to a significant improvement in the prognosis of HIV-related PCP and reduced the incidence of severe cases.

• Respiratory failure
• Pneumothorax
• Acute respiratory distress syndrome (ARDS)
• Pulmonary cyst formation
• Secondary bacterial infections

• Haematogenous spread of the infection can affect the bone marrow, liver, spleen, lymph nodes, gut, and eyes.

• Restricted access to care, which can significantly impact outcomes.