Setomelannoma rostrata Helminthosporum haledes Exserohilum rostratum
Summary
Setomelanomma rostrata/Heminthosporum haledes/Exserohium rostratum are members of the Bipolaris complex, which has been the subject of some taxonomical confusion. Fungal species from this group are ubiquitous in the environment and are mainly plant pathogens. However, a few species cause mycotic fungal disease in humans, mainly in immunosuppressed patients. Exserohilum spp. are predominantly found in tropical and subtropical regions. Heminthosporum and Exserohilum spp. – specific allergens can cause asthma, allergic rhinitis, and sinusitis. However, there are no recognized allergens currently described.
Epidemiology
Worldwide distribution
Exserohium species are ubiquitous in the environment and have a geographical distribution mainly limited to the tropics and subtropical regions. A study from India reported a prevalence of sensitization to Helminthosporm spp., as detected by skin prick test, of 1.9% amongst a cohort of patients with atopy. A study from the Midwestern USA also reported sensitization rate (of allergen-specific IgE) to H. haledes of 5%.
Route Of Exposure
Main
Exposure to the E. rostratum allergen is thought to be through the inhalational route. It has been demonstrated that approximately 13% (+/- 2.4%) of E. rostratum spores release allergen before germination. The same study also showed a significant increase in the percentage of spores releasing allergen after germination (89.9% +/- 2.7%; P<0.01). It has been proposed that a significant factor in exposure is related to the ability of fungal spores to germinate in the respiratory tract.
Clinical Relevance
Helminthosporum spp. are known to be a cause of allergic rhinitis and asthma. Furthermore, Exserohilum spp. are reportedly the cause of allergic bronchopulmonary disease. There is also a body of evidence in the literature, mainly as case reports, that Exserohilum spp. are a cause of chronic allergic fungal sinusitis. Although it should be noted that in some of these reports, no skin testing or allergen-specific IgE assay was undertaken.
Cross-Reactivity
A study from Southern China found that in patients with allergic bronchopulmonary aspergillosis and Aspergillus fumigatus-sensitized patients with asthma, H. Haledes-specific IgE levels correlated with total A. fumigatus-specific IgE (rs = 0.585, P <.05), which was consistent with the findings of a previous Swedish study. This suggests cross-reactivity of H. halodes with the A. fumigatus allergen. However, no significant correlation was found with the A. fumigatus components Asp f 1, Asp f 2, Asp f 3, Asp f 4 or Asp f 6.
References
- Levetin E, Horner WE, Scott JA, Barnes C, Baxi S, Chew GL, et al. Taxonomy of Allergenic Fungi. The Journal of Allergy and Clinical Immunology: In Practice. 2016;4(3):375-85.e1.
- Reedy JL, Negoro PE, Feliu M, Lord AK, Khan NS, Lukason DP, et al. The Carbohydrate Lectin Receptor Dectin-1 Mediates the Immune Response to Exserohilum rostratum. Infect Immun. 2017;85(3).
- Alajmi S, Koratum RM, Khan Z, Ahmad S, Jeragh A, Ibrahim H, et al. Allergic Fungal Sinusitis Caused by Exserohilum rostratum and Literature Review. Mycopathologia. 2019;184(1):89-96.
- Life Co. Exserohilum rostratum (Drechsler) K.J. Leonard & Suggs 2021 [cited 2022 10.01.22]. Available from: https://www.catalogueoflife.org/data/taxon/3DQLF.
- Dey D, Mondal P, Laha A, Sarkar T, Moitra S, Bhattacharya S, et al. Sensitization to Common Aeroallergens in the Atopic Population of West Bengal, India: An Investigation by Skin Prick Test. International Archives of Allergy and Immunology. 2018;178:1-6.
- Benninger MS, Daly T, Graffmiller K. Positivity rates of in vitro inhalant/respiratory and food allergy tests in the northern midwestern United States. Ear Nose Throat J. 2018;97(9):296-322.
- Green BJ, Mitakakis TZ, Tovey ER. Allergen detection from 11 fungal species before and after germination. J Allergy Clin Immunol. 2003;111(2):285-9.
- Luo W, Hu H, Wu Z, Wei N, Huang H, Zheng P, et al. Molecular allergen sensitization of Aspergillus fumigatus between allergic bronchopulmonary aspergillosis and A fumigatus-sensitized asthma in Guangzhou, Southern China. J Clin Lab Anal. 2020;34(10):e23448.