Pneumocystis jirovecii Pneumonia in the Intensive Care Unit: A Case Series

Abstract

Pneumocystis jirovecii pneumonia (PCP) remains a significant cause of respiratory failure in immunocompromised hosts. While historically associated with HIV infection, PCP is increasingly recognized in non-HIV immunosuppressed populations, often with distinct clinical courses. We report two critically ill PCP patients—one HIV-positive and one HIV-negative—highlighting differences in presentation, diagnosis, management, and outcomes

Introduction

Pneumocystis jirovecii, previously known as Pneumocystis carinii, is an opportunistic fungal pathogen that causes PCP—a life-threatening pneumonia in immunocompromised individuals. The incidence of PCP in HIV populations has declined with antiretroviral therapy (ART) and prophylaxis, yet it remains a vital diagnosis(1). Non-HIV immunosuppression, including corticosteroids, hematologic malignancies, and transplantation, has emerged as a major risk group, often with atypical clinical features and poorer outcomes.

Case report

Patient- 1

A 50-year-old man with a previously diagnosed immune thrombocytopenia (ITP), receiving oral corticosteroid therapy, was admitted to the ICU with history of fever with cough and expectoration for 5 days. He was initially managed in outside hospital and referred to our hospital ICU in view of worsening hypoxia. On arrival to ICU he was hypoxic requiring high flow nasal oxygenation. CT chest done on admission showed bilateral diffuse GGO. He was started on Inj. Cefoperazone sulbactum and Inj.Doxycyline. Oral steroids was replaced with IV steroids as an equivalent dose. His sputum cultures grew no pathogen and AFB stain was negative. He was empirically started on Tab. Cotrimoxazole. In view of clinical worsening and no definitive cultures, we proceeded with bronchioalveolar lavage, which finally show positive for PCP. Tab. Cotrimoxazole was changed into injectable Cotrimoxazole. He had a progressive worsening hypoxia for which he was intubated on day 8 of ICU stay. He underwent two sessions of proning. He had a progressively worsening hypoxia, hence poor prognosis explained to patient attenders. On day 11 of ICU stay he developed cardiac arrest and was declared death.

Patient- 2

A 25 years old male with no known comorbidities, presented to the ICU with history of intermittent low grade fever associated with cough and expectoration for the past 2weaks. He had an episode of hemoptysis. He initially consulted outside hospital, performed CT chest which revealed bilateral diffuse consolidation. On arrival in ICU, he was hypoxic requiring 2 litres of oxygen via nasal prongs. His hypoxia worsened gradually over the next few hours necessitating the need for initiation of HFNO. He was tested positive for HIV infection. On day 2 of admission broncho alveolar lavage was done which  showed  positive  for  PCP.  He  was  started  on  Injection

Cotrimoxazole with steroids. He was gradually weaned to oxygen via nasal prongs and shifted to ward.

Discussion

Pneumocystis jirovecii pneumonia (PCP) continues to pose a major clinical challenge across diverse immunocompromised populations, particularly in critical care settings. Although historically regarded as an AIDS-defining illness, the epidemiology of PCP has shifted over the past two decades. With widespread antiretroviral therapy (ART) and effective prophylaxis, the incidence of HIV- associated PCP has declined, whereas the burden among HIV-negative immunosuppressed patients has increased markedly. This changing landscape demands a nuanced understanding of the similarities and differences in pathophysiology, clinical manifestations, diagnostic considerations, and ICU outcomes across patient groups.

Difference in epidemiology

With the increased use of ART and cotrimoxazole prophylaxis in HIV positive patients, the incidence of PCP has reduced by 80%. Risk of PCP is greatest when CD4 < 200cells/µL.

Incidence of PCP infections is steadily increasing in HIV negative patients. Patients with prolonged use of steroids (>20mg of prednisolone for >4 weeks), hematological malignancy, post solid organ transplant, post stem cell transplant and on biologics like rituximab are at high risk(2).

Differences in Immunopathogenesis

The immune deficits predisposing to PCP differ significantly between HIV-positive and HIV-negative individuals.

In HIV infection, the hallmark is a profound CD4+ T-cell depletion. The gradual decline in cell-mediated immunity results in a slower onset of symptoms because the inflammatory response within the alveoli is relatively muted. Lower inflammatory injury paradoxically allows organisms to proliferate extensively before symptoms intensify.

In non-HIV immunosuppression, host immunity may be compromised via corticosteroids, cytotoxic drugs, biologic agents, transplantation, or hematological malignancies. Here, the immune dysfunction involves multiple pathways (e.g., impaired macrophage function, altered cytokine signaling). Because inflammatory responses remain partially intact, lung injury develops abruptly, leading to severe hypoxemia and fulminant respiratory failure within days rather than weeks(3).

These differing inflammatory responses explain why HIV patients often present subacutely, whereas non-HIV patients deteriorate rapidly and frequently progress to ARDS.

Clinical Presentation and Disease Severity

HIV-positive patients tend to present with several weeks of low- grade fever, dry cough, and progressive dyspnea. Their disease course often allows timely recognition and initiation of therapy before critical respiratory collapse(4).

HIV-negative patients frequently show acute respiratory failure, severe hypoxemia, and extensive ground-glass opacities on imaging at initial presentation. ICU admission is more common, and mortality is significantly higher.

Studies consistently demonstrate mortality rates of 30–50% in non-HIV PCP, compared with 10–20% in HIV-associated PCP, even with optimal therapy. Several factors account for this gap: delayed diagnosis, rapid disease progression, high inflammatory burden, and multiple concurrent comorbidities(5).

Diagnostic Challenges in ICU Settings

Diagnosing PCP in critically ill patients remains difficult, particularly among HIV-negative individuals where clinical suspicion is often lower.

Microbiological detection: BAL PCR assays are particularly useful in non-HIV patients, in whom the sensitivity of conventional microscopy with staining is significantly lower than in patients with HIV. Bronchoalveolar lavage and induced sputum provide the highest diagnostic sensitivity and specificity. When these samples are unavailable, PCR may be performed on upper respiratory tract specimens (eg, nasopharyngeal aspirates or oral washes), although both false-positive and false-negative results may occur. In such cases, careful clinical correlation is required to distinguish colonization from true lower respiratory tract infection. PCR of BAL fluid or induced sputum can increase the diagnostic yield over conventional staining alone in immunocompromised patients without HIV.

Biomarkers: β-D-glucan is a useful adjunctive test with high sensitivity, but lacks specificity and may be elevated in many invasive fungal infections.

Imaging: While diffuse bilateral ground-glass opacities are characteristic, non-HIV patients more frequently exhibit additional abnormalities such as septal thickening, consolidation, or cyst formation, which may mimic ARDS, viral pneumonias, or drug-induced lung injury.

Treatment Response and Corticosteroid Use

TMP-SMX remains the standard therapy across both groups, yet response patterns vary.

In HIV-positive PCP, the use of adjunctive corticosteroids is strongly supported by evidence, as they dampen the intense inflammatory response that occurs after antimicrobial-mediated organism lysis. Steroids reduce mortality and need for mechanical ventilation in moderate to severe disease(6,7).

In HIV-negative PCP, the role of corticosteroids is less clear. While commonly used in severe hypoxemia or ARDS, strong evidence is lacking, and potential harm may occur in certain immunosuppressed states. Nevertheless, many clinicians adopt corticosteroids empirically in severe cases due to high inflammatory burden.

ICU Management Complexities

PCP is one of the most common infectious causes of respiratory failure requiring mechanical ventilation in immunocompromised patients.

Key challenges include(8):

• profound hypoxemia requiring high FiO₂
• risk of barotrauma due to cystic lung changes
• rapid evolution to ARDS
• concurrent infections (bacterial, viral, fungal)
• complications from immunosuppression, including delayed recovery

Outcome Differences and Prognostic Factors

Several studies confirm that HIV-negative patients experience worse outcomes due to (9):

• higher inflammatory injury
• increased need for invasive ventilation
• greater incidence of multi-organ dysfunction
• delayed diagnosis due to low initial suspicion

In contrast, HIV-positive patients often stabilize with prompt anti-PCP therapy and supportive care, especially if ART is reinitiated early.

Importance of Prophylaxis

Prophylaxis remains central to reducing PCP incidence.

• HIV-positive individuals   with   CD4   < 200   cells/µL   benefit greatly from TMP-SMX prophylaxis (10).
• HIV-negative at-risk populations—those on high-dose steroids, biologics, stem-cell transplant recipients, and hematologic malignancy patients—should be evaluated carefully for prophylaxis.

The shift in epidemiology underscores the importance of strong prophylactic strategies in non-HIV immunosuppressed patients

Conclusion

This case series demonstrate that PCP in the ICU requires high suspicion across varied immunosuppressed populations. Early diagnosis and aggressive management improve outcomes, but disease trajectory differs significantly between HIV and non-HIV patients. Awareness and prophylaxis strategies should be tailored to at-risk groups.

References

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