Identification of fungi causing humidifier lung: 2 rare cases and a review of the literature

Abstract

Background Humidifier lung (HL) is a hypersensitivity pneumonitis resulting from exposure to humidifiers, with fungi from the humidifier as one of the etiologic agents. However, identification of the fungal species responsible for each case can be challenging because of difficulties in culturing fungi, their accurate identification, and interpreting the results of specific serum IgG testing. Objective To clarify the best way to determine the causative fungal species of each HL case. Methods We report 2 cases with HL in which rare fungi were identified as causative agents. In addition, we searched MEDLINE for previous publications on HL caused by fungi and performed a literature review focusing on clinical testing for the determination of causal fungal species. Results In our 2 cases, we identified Fusarium oxysporum species complex, Purpureocillium lilacinum, Acremonium sclerotigenum/egyptiacum as the causative fungal species, based on findings that these could be cultured from humidifier water (HW) and precipitins against these fungi were also positive. The literature review identified 31 HL cases in which the causative fungal species had been documented. In more than half of the cases (17 of 31) there was a concordance between the fungal species cultured from HW and the presence of specific IgG in the blood. Conclusion We recommend performing culture of fungi from HW and specific serum IgG testing for the accurate determination of the causative fungal species in HL, and concordance between them serves as a rationale for the determination of causative fungal species.

Asia Pacific Allergy : Asia Pacific and beyond

“…In this issue, readers will find an excellent review article on the mechanisms and biomarkers of successful allergen-specific immunotherapy [ 6 ]. Readers will also find nice original articles such as a 5-year longitudinal study on the Melbourne epidemic thunderstorm asthma event 2016 [ 7 ], natural history and clinical course of patients with dermographism in a tropical country [ 8 ], how physicians approach hereditary angioedema [ 9 ], a study on anaphylaxis after Coronavac vaccination in healthcare workers [ 10 ], the level of knowledge among healthcare professionals regarding anaphylaxis [ 11 ], identification of fungi causing humidifier lung [ 12 ], and the measures for food allergy emergency in nurseries [ 13 ]. Reader will be interested in the case reports such as a clindamycin graded challenge in an AIDS patient [ 14 ], a case of hypereosinophilic syndrome with gastrointestinal involvement showing tissue eosinophil cytolysis [ 15 ], and severe chronic cough relating to post-COVID-19 interstitial lung disease [ 16 ].…”