Menthol-Flavored Cigarettes: Potentially a Strong Trigger of Acute Eosinophilic Pneumonia
Menthol-flavored cigarettes recently have received significant attention. Lower quit rates and higher relapse rates of smoking in people who smoke menthol-flavored cigarettes have been demonstrated.1 Additional disadvantages of menthol cigarettes also might exist. We present a lesson learned from a case we experienced: Menthol cigarette smoking might be a stronger trigger of acute eosinophilic pneumonia compared with nonflavored cigarette smoking.
A 19-year-old man visited our hospital with a 3-day history of dry cough, dyspnea, and high fever. He had been completely healthy until the appearance of these symptoms. He had started smoking menthol cigarettes approximately 1 month before his visit to our hospital. He had no history of lung disease. He had no obvious history of occupational dust inhalation or illegal drug use. When he visited our outpatient department, his oxygen saturation was 88% while breathing room air. His temperature was 38.8°C.
His complete blood count and blood chemistry findings were unremarkable, except for elevations in white blood cell count (14,900/μL), C-reactive protein (11.45 mg/dL), serum surfactant protein-D (259 ng/mL), and immunoglobulin-E (437 IU/mL). Chest x-ray and computed tomography scan showed patchy shadows and infiltration in both lungs and thickening of interlobular septa (Figure, A, B). Bronchoalveolar lavage findings showed marked elevation of eosinophils (total cell count 12.7 × 105/mL, eosinophils 67.6%) (Figure, C). The bronchoalveolar lavage eosinophil elevation, typical radiologic findings, and clinical history of symptom onset after initiation of cigarette smoking suggested a diagnosis of acute eosinophilic pneumonia.
Systemic corticosteroid therapy resulted in resolution of his symptoms and radiologic findings (Figure, D). The patient was advised to stop smoking, but continued to smoke nonflavored cigarettes against the advice. Recurrence of acute eosinophilic pneumonia was not observed with smoking of nonflavored cigarettes.
Although acute eosinophilic pneumonia is known to be triggered by the initiation of cigarette smoking, acute eosinophilic pneumonia cases triggered by inhalation or intake of only menthol have not been reported. It is speculated that menthol facilitates the triggering of acute eosinophilic pneumonia by the initiation of smoking rather than directly triggering acute eosinophilic pneumonia itself. Some reported cases of acute eosinophilic pneumonia developed after switching from smoking nonflavored cigarettes to menthol-flavored cigarettes.2, 3, 4Our patient, as well as a previously reported patient,5 continued to smoke nonflavored cigarettes against the doctor’s advice to quit smoking after resolution of the acute eosinophilic pneumonia triggered by menthol-flavored cigarettes, with no relapse of acute eosinophilic pneumonia after reinitiation of smoking. This fact indicates that menthol may be involved in increased sensitivity to acute eosinophilic pneumonia triggered by smoking.
The pharmacologic effects of menthol on the airway are still under investigation. Inhalation of menthol vapor is reported to increase cough thresholds.6 Stimulation of TRP melastatin 8, a menthol receptor, induces inflammation.7 The former effect of menthol leads to retention of the toxic dust of cigarette smoke in the smoker’s airway, and the latter induces lung inflammation, which facilitates the development of acute eosinophilic pneumonia. Further research is required to clarify the association between menthol and acute eosinophilic pneumonia.
As a significant number of young adults initiate smoking menthol-flavored cigarettes, the risk of menthol in triggering acute eosinophilic pneumonia needs to be highlighted.
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-Naoto Ogura, MD, Yuta Kono, MD, PhD, Masako To, MD, PhD, Shintaro Mikami, MD, Seiko Soeda, MD, PhD, Hiroko Hara, MD, Yasuo To, MD, PhD
This article originally appeared in the February 2017 issue of The American Journal of Medicine.