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QJM
QJM
qjmedj
QJM: An International Journal of Medicine
1460-2725
1460-2393
Oxford University Press

38588570
10.1093/qjmed/hcae066
hcae066
Case Report
AcademicSubjects/MED00010
A case of cholesterol crystals detected in 37-year pleural effusion
Hu Y Writing - original draft Fengdu General Hospital, Pulmonology Department, Chongqing, China

https://orcid.org/0009-0002-4335-715X
Zhang J Fengdu General Hospital, Pulmonology Department, Chongqing, China

Address correspondence to J. Zhang, Fengdu General Hospital, Pulmonology Department, Chongqing, China. email: 13896669865@163.com
8 2024
08 4 2024
08 4 2024
117 8 601602
29 3 2024
26 4 2024
© The Author(s) 2024. Published by Oxford University Press on behalf of the Association of Physicians.
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
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pmcLearning points for clinicians In clinical practice, regardless of whether the patient has conditions like tuberculosis or rheumatic disease, it is crucial to identify and actively intervene early to prevent chronic pleural inflammation due to long-term fluid retention. While the presence of cholesterol crystals in pleural effusion is extremely rare, clinicians should consider pseudochylothorax in the differential diagnosis of unexplained pleural effusions.

A male patient, 68 years old, who has had a long-standing occupation in agriculture, presented with the chief complaint of ‘shortness of breath after activity with cough for over a month’. Past medical history: 37 years ago, the patient underwent thoracentesis for pleural effusion, but only a small amount of fluid was removed for unknown reasons and specifics about the volume and nature of the fluid are unknown. No follow-up chest CT was conducted. The patient denies any history of tuberculosis and has not taken any antitubercular medications. Seven years ago, a chest X-ray performed at a local clinic revealed a left-sided pleural effusion (report not seen), and no treatment was provided. Physical examination: Left chest wall retraction, diminished breath sounds on the left lung, decreased vocal fremitus, dullness to percussion on the left hemithorax, and few moist rales on the right lung. Heart rhythm was regular with no pathological murmurs. Joint examinations were unremarkable.

Auxiliary examinations: At admission, the following results were obtained—white blood cell count: 4.1 × 109/L, platelets: 229 × 109/L, eosinophils: 0.14 × 109/L. Serum tumor markers is normal. Antinuclear antibody spectrum, anti-CCP antibodies, rheumatoid factor, and complete rheumatology immune panel all normal. Tuberculosis bacterium IgG antibody was negative. Sputum and pleural fluid acid-fast staining, fungal immunofluorescence staining, and tuberculosis branch bacillus DNA all were negative. Cholesterol crystals were observed under the microscope in the pleural fluid (Figure 1). Pleural fluid lipid profile: triglycerides 0.16 mmol/L, cholesterol 2.03 mmol/L, high-density lipoprotein (HDL) 0.57 mmol/L, and low-density lipoprotein (LDL) 0.95 mmol/L.

Figure 1. (a) Appearance of the first pleural fluid, which was yellow and celiac in color.(b) Shows the electron microscope image under 40 × 40 high magnification, which is characterized by ‘square or irregular square’.

Discussion

Cholesterol pleural effusion, also known as pseudochylothorax, is a rare form of pleural effusion that is characterized by a lipid-rich exudate containing cholesterol crystals. This contrasts with chylothorax, which is also a lipid-rich effusion but contains chylomicrons instead of cholesterol crystals, marking the fundamental difference between the two.1 In pseudochylothorax, the cholesterol levels can reach up to 200 mg/dL (5.2 mmol/L), while triglyceride levels usually remain below 50 mg/dL (0.56 mmol/L). In some cases, triglyceride levels may increase, but the ratio of cholesterol to triglycerides in the pleural fluid is always greater than 1.2 Cholesterol crystals are quite rare pathological findings, appearing under the microscope as notched or irregularly shaped transparent square crystals. Epidemiological studies are confined to case reports and literature reviews, with over a hundred cases having been reported internationally.3 A meta-analysis showed that males accounted for 71.9% of the cases, with the main causes being tuberculosis, rheumatoid arthritis, chronic pneumothorax, and chronic hemothorax, followed by parasitic infections such as paragonimiasis and echinococcosis.4 Even rarer causes is COVID-19.5

In this particular case, the patient had no tuberculosis, parasites, rheumatoid arthritis, or tumors. Therefore, the patient’s cholesterol effusion is still considered to be due to chronic inflammation and prolonged retention of effusion, resulting in cholesterol crystallization which is closely related to long-term stimulation by chronic non-specific inflammation.

Author contributions

Yahong Hu (Writing—original draft [equal])

Conflict of interest

None declared.
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References

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