Silent threat: A case report of acute fulminant exogenous lipoid pneumonia leading to severe ARDS

Abstract

Exogenous lipoid pneumonia (ELP) is a rare pulmonary disorder resulting from the aspiration or inhalation of exogenous lipid substances. While most documented cases follow an indolent, chronic course and are associated with favorable outcomes, fulminant postoperative ELP remains exceedingly uncommon—often presenting with rapid respiratory decompensation that may clinically and radiologically mimic severe community-acquired pneumonia or acute respiratory distress syndrome (ARDS). We report a 61-year-old man with occult fulminant postoperative ELP after repeated oral liquid paraffin use for bowel obstruction caused by a large rectal neoplasm. No definite aspiration event was witnessed. After emergency diverting ileostomy, he developed rapidly progressive refractory hypoxemia with bilateral ground-glass opacities and consolidations on chest CT. BALF pathogen testing was largely negative, although a positive galactomannan result meant that fungal coinfection could not be fully excluded. Oil Red O staining demonstrated lipid-laden macrophages, supporting the diagnosis of ELP. Despite invasive mechanical ventilation, prone positioning, segmented alveolar lavage, systemic corticosteroids, adjunctive IVIG, respiratory failure progressed. The patient died three days after discharge against medical advice, most likely from progressive respiratory failure. This case highlights a rare and fulminant form of postoperative exogenous lipoid pneumonia following liquid paraffin exposure for bowel obstruction. Early recognition is important because ELP may coexist with infection and can progress rapidly despite intensive supportive care.

Introduction

Exogenous lipoid pneumonia (ELP) is caused by aspiration or inhalation of oily substances, including mineral oils, petroleum jelly, olive oil, mentholated topical ointments, hydrocarbons, polyethylene glycol, and oil-based cosmetic products.^1–6 Once oily particles enter the alveoli, they are phagocytosed by macrophages and may trigger persistent inflammation, tissue injury, and fibrosis. ⁷ Because the clinical and radiological manifestations are nonspecific, ELP often mimics infectious pneumonia, malignancy, or ARDS, and diagnosis is frequently delayed. ⁸ Bronchoalveolar lavage (BAL) showing lipid-laden macrophages with fat staining is highly supportive of the diagnosis.^9,10 Treatment is not standardized. Management usually includes discontinuation of the offending oil, aspiration precautions, supportive respiratory care, and, in severe cases, consideration of corticosteroids and lavage-based strategies.^7,8,11 Fulminant ELP with ARDS has been reported previously ⁸ ; therefore, the novelty of the present case is not ARDS itself but the postoperative onset after bowel obstruction surgery, the preceding liquid paraffin exposure, and the unusually rapid deterioration in an ICU setting.

Case report

This case report was prepared and reported in accordance with the CARE guideline, ¹² and the completed CARE checklist is provided as a supplementary file.

A 61-year-old man with no known previous medical history presented to the Emergency Department with a five-day history of progressive abdominal pain and cessation of bowel movement. Abdominal computed tomography (CT) revealed marked colonic dilatation, rectal wall thickening, and luminal narrowing (Figure 1A). Colonoscopy revealed a large annular neoplasm located approximately 3 cm proximal to the anal verge (Figure 1B). The initial diagnosis was bowel obstruction caused by a rectal tumor. Prior to surgery, the patient received oral liquid paraffin (50 mL) three times daily for approximately five days to alleviate constipation and yielding a 6-hour interval between the last dose and surgical intervention, and no choking or aspiration episode was directly witnessed during hospitalization.

Figure 1.

Multi-modality imaging of the patient. (A) Abdominal CT showing marked colonic dilatation. (B) Colonoscopy showing a large neoplasm located 3 cm proximal to the anal verge. (C) Serial chest CT showing progression of bilateral ground-glass opacities and consolidations from pre-surgery to POD 15. POD denotes postoperative day. (D) Oil Red O staining of BALF cytology showing large lipid droplets within macrophages.

Given persistent bowel obstruction despite conservative management, the patient underwent emergency diverting ileostomy without tumor resection or bowel anastomosis and was transferred to the intensive care unit (ICU). The ileostomy functioned satisfactorily, and the tracheal tube was removed on postoperative day (POD) 2. However, progressive hypoxemia despite high-flow nasal cannula oxygen therapy and awake prone positioning required reintubation and invasive mechanical ventilation on POD 4.

Preoperative chest CT showed scattered bilateral ground-glass opacities, whereas postoperative chest CT showed rapidly progressive diffuse infiltrates and multiple pulmonary acinar shadows (Figure 1C). Fiberoptic bronchoscopy with BAL of the right lower lobe showed normal endobronchial anatomy without purulent secretions or hemorrhage. All pathogenic organisms were negative in BALF, including bacterial, fungal, viral, and atypical pathogens. Empirical broad-spectrum antibacterial therapy with cefoperazone/sulbactam was administered for suspected postoperative hospital-acquired/aspiration-related pneumonia, rather than community-acquired pneumonia. Intravenous methylprednisolone 40 mg daily was initiated because of severe inflammatory lung injury and refractory hypoxemia, with markedly elevated inflammatory markers (IL-6 >1000 pg/mL and hsCRP >304 mg/L; Figure 2). BALF galactomannan test was positive (GM 4.31, cutoff >0.80 S/CO), so antifungal therapy including amphotericin B and voriconazole was added. Although combination antifungal therapy is not routine practice, amphotericin B plus voriconazole was used empirically because invasive fungal infection could not be excluded in this critically ill patient with a strongly positive BALF GM result and rapidly progressive respiratory failure. This was an individualized decision made before diagnostic clarification. Despite antibacterial, antifungal, and steroid therapy, respiratory failure worsened, with a PaO₂/FiO₂ ratio below 200 mmHg and lung compliance decreasing to 21 mL/cmH₂O. After multidisciplinary discussion, ELP was suspected because of the preceding repeated oral liquid paraffin exposure. Oil Red O staining of BALF demonstrated large lipid droplets in macrophages (Figure 1D), supporting the diagnosis of ELP. After ELP was diagnosed, methylprednisolone was increased to 40 mg twice daily for acute lung injury. Intravenous immunoglobulin (20 g daily for three days) was administered as an individualized adjunctive immune-supportive therapy for the persistent lymphocytopenia(absolute lymphocyte counts: 0.08-0.70✕10⁹/L, cutoff 0.8-4.0✕10⁹/L) with lymphocyte subset analysis showed decreased absolute counts of T cells, CD4+ T cells (403/ul, cutoff 561-1137/ul), CD8+ T cells (58/ul, cutoff 404-754/ul), B cells(176/ul, cutoff 180-324/ul), and natural killer cells(60/ul, cutoff 175-567/ul); however, this use was empirical, and evidence supporting IVIG for ELP remains limited.

Figure 2.

Timeline of inflammatory indicators and treatments. IL-6, interleukin-6; CRP, C-reactive protein; P/F, PaO2/FiO2; T, temperature; WBC, white blood cell.

On POD 7, chest CT showed worsening bilateral diffuse infiltrates and lung compliance decreased further to 16 mL/cmH₂O. Lung-protective ventilation was continued. The maximum ventilatory requirement was a fraction of inspired oxygen (FiO2) of 0.70 with positive end-expiratory pressure (PEEP) of 10 cmH₂O. Electrical impedance tomography (EIT) was used to assess regional ventilation distribution and ventilation homogeneity (Figure 3). Repeated bronchoalveolar lavage was performed on POD 11 in the right upper lobe and on POD 14 in the right middle lobe (Figure 2). Nevertheless, respiratory distress progressed, the PaO₂/FiO₂ ratio remained below 150 mmHg, and chest imaging on POD 15 showed more extensive infiltrates. The patient was discharged against medical advice at the family’s request while still experiencing severe refractory respiratory failure and died three days after discharge. Because no autopsy was performed and post-discharge records were limited, the exact terminal cause of death could not be definitively confirmed; however, death was most likely related to progressive respiratory failure.

Figure 3.

Lung ventilation assessed by electrical impedance tomography (PulmoVista 500, Drager Medical, Lubeck, Germany). Compared with the supine position, prone positioning improved the uniformity of ventilation distribution without obvious ventilation loss.

Discussion

ELP is an uncommon etiology of unresolving pneumonia resulting from the aspiration or inhalation of oil products. ⁹ Aspiration of oily substances into the lower parts of respiratory tract is the main causative factor responsible for ELP. Once oily particles reach the alveoli, they are engulfed by macrophages, where they are acted upon by lipase, which releases free fatty acids. These fatty acids can damage the pulmonary parenchyma and provoke necrotizing inflammation. Most reported cases have shown a benign prognosis. Fatal outcomes or severe respiratory distress have been rarely reported.^8,13 Here, we report a case of acute fulminant ELP induced by oral liquid paraffin for the treatment of intestinal obstruction.

Paraffin oil, a type of mineral oil, is an inert substance that is not metabolized by pulmonary enzymes when aspirated. Instead, it is emulsified and phagocytosed by alveolar macrophages, returning to the alveolar space after cell death. The release of inflammatory cytokines by the activated macrophages probably leads to high inflammatory response. ¹⁴ In this case, high inflammatory response was particularly noticeable in the early stage, including IL-6>1000pg/ml and hsCRP>304mg/ml, which resulted in high respiratory drive during mechanical ventilation. Moreover, the cytological classification of BALF in patients with ELP was predominantly neutrophilic (nearly 65%), ⁶ however, our patient failed to acquire the cytological classification for viscous BALF. Another phenomenon was that EIT showed satisfactory lung ventilation, but the lung compliance was progressively decreasing, which indicated diffused interstitial lung damage.

Clinically, the diagnosis of ELP remains highly challenging. Due to non-specific symptoms and massive consolidation that were mimicing infectious pneumonia or lung cancer, the misdiagnosis was particularly high. ¹³ The diagnosis mainly involved in a long-term history of exposure to oil and the presence of lipid-laden macrophages on bronchoalveolar lavage (BAL) analysis. ⁹ Here, we illustrated the diagnostic difficulty of fulminant ELP as no aspiration or choking event was witnessed. Besides, the positive BALF galactomannan resulted in complicated interpretation indicating the unresolved ARDS was not solely caused by ELP. Possible invasive fungal infection, colonization, false positivity, and ELP-related inflammatory lung injury were considered. However, the combination of repeated oral liquid paraffin exposure before surgery, rapid postoperative radiological progression, negative routine pathogen tests, and Oil Red O-positive macrophages strongly supported ELP as a major contributor to the clinical course.

There are no established strategies of treatment, but the most important is the identification and discontinuation of the offending oil.^7,15 One week after discontinuing paraffin oil therapy, the patient’s imaging still showed rapid progression, and the respiratory mechanics indicated a significant decrease in lung compliance. The use of steroids was controversial and should be reserved for critical care patients.^8,16 In addition, whole lung lavage may also be therapeutic. ⁸ Most of reported cases were long-term exposure to irritant agents and owned well prognosis after administration of steroids. ¹⁷ In our case, patient demonstrated rapidly progressive respiratory failure simulating ARDS, however, timely intervention with large dose of intravenous steroids, IVIG and bronchoalveolar lavage all failed. A potentially large occult aspiration burden, an intense inflammatory response, and delayed recognition of ELP may have contributed to the fatal outcome.

This report also has limitations. First, the exact dose of liquid paraffin and the exact time interval between the final dose and surgery require confirmation from the original medical record. Second, no aspiration event was witnessed. Third, BALF cytological classification was not obtained because samples were excessively viscous. Finally, without autopsy, the precise terminal cause of death could not be proven.

Conclusion

This case highlights a rare and fulminant form of postoperative exogenous lipoid pneumonia following liquid paraffin exposure for bowel obstruction. The disease developed insidiously without a witnessed aspiration event but progressed rapidly to refractory respiratory failure. Clinicians should recognize that occult paraffin aspiration may cause rapidly fatal postoperative ELP, and early suspicion is crucial when unexplained respiratory failure occurs after paraffin exposure.

Appendix.

Abbreviations

BALF

bronchoalveolar lavage fluid

GM

galactomannan

IL-6

interleukin-6

hsCRP

high-sensitivity C-reactive protein

PaO₂/FiO₂

ratio of arterial oxygen partial pressure to fraction of inspired oxygen

IVIG

intravenous immunoglobulin

FiO₂

fraction of inspired oxygen

PEEP

positive end-expiratory pressure

EIT

electrical impedance tomography.

ORCID iD

Na Wang https://orcid.org/0000-0002-3760-5420

Ethical considerations

This case report was conducted in accordance with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Peking Union Medical College Hospital (Approved date: Aug 2, 2022; No. I-22PJ140).

Consent to participate

Written informed consent was obtained from the patient’s next of kin because the patient was intubated, sedated, and unable to provide consent personally.

Consent for publication

Written informed consent for publication of the patient’s clinical details and images was obtained from the patient’s next of kin.

Data Availability Statement

All data relevant to this case report are included in the article. Additional anonymized information may be available from the corresponding author upon reasonable request, subject to institutional requirements.*