Onychomycosis is a common nail infection. Terbinafine-resistant dermatophyte infections pose an emerging global public health concern, but few cases have been described in the United States. We retrospectively reviewed and characterized clinical, histopathological, and mycological features of patients with mycologically confirmed onychomycosis who failed oral terbinafine treatment for onychomycosis at a U.S. academic nail referral center and ascertained for terbinafine-resistant isolates. During 1 June 2022–31 January 2023 at Weill Cornell Medicine in New York City, USA, 96 patients with mycologically confirmed onychomycosis were treated with oral terbinafine. Among 64 patients with adequate follow-up, 36 had clinical or complete cure. Of 28 patients who failed treatment, 17 underwent terbinafine resistance testing. Trichophyton rubrum with terbinafine resistance-conferring mutations was isolated from two patients. Overall, terbinafine failures for onychomycosis were relatively common, with some cases associated with terbinafine-resistant T. rubrum infections. These findings underscore the need for a clinical awareness of this emerging problem and public health efforts to monitor and prevent spread. We highlight the importance of diagnostic testing and species identification for onychomycosis patients and the increasingly important role of fungal identification and susceptibility testing to guide therapy.
Introduction: Localized longitudinal erythronychia is defined as a single nail with a longitudinal red band extending the length of a nail plate. It has a broad differential of benign and malignant etiologies, and is rarely due to benign vascular proliferations. Case Presentation: We present a unique case of nail unit arteriovenous hemangioma presenting as longitudinal erythronychia of the left thumbnail in a 76-year-old male. The band was 6 mm and encompassed over 40% of the surface area of the nail plate. Dermoscopy showed red bands that were regular in terms of color, but not thickness or spacing. Due to concern for an amelanotic melanoma, a longitudinal excision was performed. Histopathology was consistent with a diagnosis of nail unit arteriovenous hemangioma. Conclusion: Arteriovenous hemangiomas were rarely present in the nail unit. They can be present as a blue or red nodule/macule, or as longitudinal erythronychia. Diagnosis often requires an excisional biopsy, with histopathology notable for a proliferation of multiple thick- and thin-walled vascular structures lined by a flattened endothelium. Our case emphasizes the need to consider vascular proliferations, such as arteriovenous hemangioma, in the differential diagnosis of longitudinal erythronychia.
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