Cytokine levels and pathological characteristics of a patient with severe coronavirus disease 2019: a case report

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Cytokine levels and pathological characteristics of a patient with severe coronavirus disease 2019: a case report

Severe COVID-19 can progress from mild fatigue and fever to life-threatening respiratory failure in weeks, but the biological mechanisms driving this decline remain poorly understood. A 2022 case study from researchers at Harbin Medical University and its affiliated hospitals offers rare, detailed insight into the cytokine levels and lung pathology of a patient who died from severe SARS-CoV-2 infection—findings that could help clinicians better identify and treat high-risk patients.

The Patient’s Clinical Course

In January 2020, a 57-year-old man with no prior health issues developed fatigue and fever two days after attending a family party where a relative had traveled from Wuhan (the initial COVID-19 epicenter). Over nine days, his symptoms worsened to include a persistent cough and shortness of breath, prompting an emergency room visit. A throat swab confirmed SARS-CoV-2 infection via real-time reverse-transcription polymerase chain reaction (RT-PCR), and he was admitted to a local hospital for supportive care, antiviral drugs, inhaled interferon-g (to boost immunity), and oxygen therapy.

By February 8, his breathing deteriorated further, requiring non-invasive mechanical ventilation. Ten days later, his oxygenation index—a measure of how well the lungs deliver oxygen to the blood—dropped to 85.8 mmHg (normal is over 300 mmHg), so doctors switched to invasive ventilation. He also received antibiotics, sedatives, vasopressors (to stabilize blood pressure), and renal replacement therapy (a treatment that takes over for failed kidneys, removing waste and excess fluids). When his oxygen levels fell again the next day, he was placed on extracorporeal membrane oxygenation (ECMO)—a machine that acts as an artificial lung, pumping blood through a membrane to add oxygen and remove carbon dioxide. Despite two weeks of prone position ventilation (lying on his stomach to improve oxygen flow) and ECMO support, his vital signs remained unstable.

Key Cytokine and Immune Findings

Severe COVID-19 often triggers leukocytosis (high white blood cell counts) and elevated inflammatory markers, so the team measured the patient’s cytokines—immune system proteins that fight infection but can damage healthy tissue if overproduced. Early on, they found elevated levels of interleukin-6 (IL-6: 69.38 pg/mL) and interleukin-10 (IL-10: 32.13 pg/mL). When they started continuous renal replacement therapy to remove excess cytokines on February 23, levels spiked even higher (IL-6: 345.51 pg/mL; IL-10: 44.77 pg/mL)—a sign of a dangerous cytokine storm, where the immune system overreacts and attacks healthy cells.

They also analyzed his immune cell counts and found critically low levels of CD4+ and CD8+ T cells—key white blood cells that target viruses—at 147 and 114 cells/mL, respectively. Lymphopenia (low lymphocyte counts) is a known red flag for severe COVID-19 mortality, as these cells are essential for clearing infections.

Lung Pathology: What the Biopsy Revealed

On February 24, the patient suffered a sudden drop in blood pressure and oxygen levels. A chest CT scan revealed right hemopneumothorax (blood and air in the chest cavity), and thoracoscopy showed blood clots in his lung lobes. To investigate his pulmonary inflammation, doctors performed a right lung biopsy using ultrasound guidance on March 16.

The biopsy uncovered classic signs of severe COVID-19 lung damage:

  • Exudative inflammation: Fluid, debris, and mucus-like substances filled some alveoli (air sacs), blocking airflow and worsening low oxygen levels.
  • Interstitial inflammation: Inflammation in the tissue between alveoli, causing the alveolar septa (walls) to widen.
  • Fibrosis: Scarring in the alveolar tissue and around blood vessels.
  • Viral cytopathic changes: Atypical enlarged alveolar cells with large nuclei and pink-staining (eosinophilic) changes—signs of virus-induced cell damage.
  • Immune cell infiltration: High levels of CD68+ macrophages (activated immune cells linked to inflammation) in the alveoli and septa. Few CD8+ T cells, scattered CD4+ T cells, and no CD20+ B cells (another immune cell type) were found.

Immunohistochemical staining confirmed SARS-CoV-2 nucleoprotein in some alveolar epithelial cells, while thyroid transcription factor 1 (TTF-1) staining showed proliferation of type II alveolar cells—cells that repair lung tissue but were unable to reverse the damage.

How These Findings Fit with Existing Research

The patient’s lung pathology aligns with findings from other severe coronavirus infections like SARS (2003) and MERS (2012). All three viruses cause pulmonary edema (fluid in the lungs), consolidation (solidification of lung tissue), and hemorrhage. Microscopically, they trigger exudative alveolar damage, hyaline membrane formation (a protein layer that blocks gas exchange), and severe inflammation. The high number of CD68+ macrophages in this patient’s lungs also mirrors what’s been seen in fatal SARS cases.

Implications for Severe COVID-19 Treatment

The study’s authors note that these findings reinforce the need for personalized, early interventions for severe COVID-19:

  • Cytokine targeting: Therapies that reduce IL-6 (like tocilizumab) or other pro-inflammatory cytokines could prevent dangerous cytokine storms.
  • Immune support: Treatments that boost T cell function might help patients clear the virus before lung damage becomes irreversible.
  • Mucus clearance: Interventions to remove excess mucus and fluid from the lungs could improve oxygenation and slow progression to respiratory failure.

Consent and Funding

The patient provided written consent for his clinical information and images to be published, with efforts made to protect his identity. The research was supported by grants from the National Natural Science Foundation of China (Nos. 81770276, 81772045, and 81902000), the Heilongjiang Provincial Science and Technology Department’s Novel Coronavirus Pneumonia Emergency Treatment and Diagnosis Technology Research Project, the Nn10 Program of Harbin Medical University Cancer Hospital, and the Heilongjiang Health and Family Planning Commission (No. 2018086).

Conclusion

While this is a single case, the detailed data on cytokine levels and lung pathology offers a rare window into the final stages of severe COVID-19. For clinicians, these findings highlight the importance of monitoring cytokine levels and immune cell counts in high-risk patients. For researchers, they point to new targets for life-saving treatments—critical steps toward reducing mortality from this devastating disease.

References

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