Synopsis of key findings:
Patients with fungal otitis externa typically present with swelling and erythema of the external auditory canal and report otalgia, otorrhoea, itching and hypoacusis.1,2,5 Symptoms of itching and otorrhoea were more common in immunocompetent patients whereas otalgia, blocked sensation, decreased hearing and tinnitus were noted more in immunocompromised patients.4,6
Examination findings include oedema and serous transudate of external canal skin, erythema and perforation of a thickened tympanic membrane, as well as serous discharge from the middle ear into the external auditory canal.1
There is a consensus in the literature that the responsible pathogens were Candida and Aspergillus spp.,2,5 with the former being more common in immunocompromised patients.6
The prevalence of otomycosis is reported to be between 9%4 – 30.4%.5 The identified risk factors include humid climates, chronic otitis, lack of cerumen2 as well as extensive and unnecessary use of both topical and systemic antibiotics.2 There was also a higher incidence noted in male patients.4,6 Ho et al. found an increased risk of otomycosis with previous otological procedures, as well as the presence of a mastoid cavity.4
The study by Jackman et al was key in our understanding of the contribution of topical antibiotic drops such as Ofloxacin to the development of otomycosis. The mechanisms are two fold: it’s action as a bactericidal allowing fungal proliferation due to the lack of competing bacterial growth as well as it’s neutral pH allowing an optimal environment for fungal growth. The proposed pathophysiology was that perforations form after sub-epithelial abscess develops on the tympanic membrane. Fungus causes thrombosis in adjacent blood vessels, which produces avascular necrosis of the underlying tympanic membrane resulting in a perforation.7