Onychoscopic characteristics of Trichophyton rubrum and Trichophyton interdigitalis fungal infections: A multicentric study

Abstract

BackgroundTrichophyton rubrum and Trichophyton mentagrophytes variant interdigitalis are the most frequent etiologic agents of onychomycosis. Diagnosis of certainty requires mycological examination, which often results unfeasible.ObjectivesThe aim of our study is to describe pathogen specific dermoscopic features, allowing a differential diagnosis without the need for cultural examination, in order to prescribe the most appropriate treatment anyway.Patients and methodsWe conducted an observational retrospective study on 54 patients with a culture proven diagnosis of distal subungual onychomycosis of the toenail, caused by Trichophyton rubrum or Trichophyton mentagrophytes variant interdigitalis. Using a videodermatoscope we collected data on nail colour (white, yellow, orange, brown, dark) and on dermoscopic patterns (aurora, spikes, jagged, ruin, linear edge, dots, striae).ResultsFifty‐four patients, with a total of 72 nails, were eligible for this study. Analysing the association between discoloration of the nail plate and type of infection (T. rubrum or T. interdigitalis), no correlation turned out to be statistically significant. Instead, significant associations between spikes and T. rubrum infection and striae and infection from T. interdigitalis were identified. Finally, a 100% specificity was identified for white colour and ruin pattern for T. rubrum infection, and brown colour, jagged border and aurora pattern for T. interdigitalis.ConclusionsTrying to find relationships between specific pathogens and dermoscopic patterns, we found out an association between spikes and striae and T. rubrum and T. interdigitalis respectively. Further larger studies are however necessary to evaluate our preliminary findings.

Comparison of dermoscopic characteristics on toenail onychomycosis in psoriatic and non‐psoriatic patients: A prospective study

“…This study's observation that only 59.91% of toenail OM cases exhibited nail spikes emphasizes the importance of not excluding OM solely based on the absence of this feature. Starace et al 5 . reported significant associations between spikes and Trichophyton rubrum infection and striae and infection from Trichophyton interdigitalis .…”

“…16,17 This study's observation that only 59.91% of toenail OM cases exhibited nail spikes emphasizes the importance of not excluding OM solely based on the absence of this feature. Starace et al 5 reported significant associations between spikes and Trichophyton rubrum infection and striae and infection from Trichophyton interdigitalis. We cannot analyze the correlation between the dermoscopic features and the pathogen type because only a few isolates for Trichophyton interdigitalis were captured in this study.…”

“…However, achieving a definitive diagnosis often faces challenges, as it requires direct fungal examination, culture or nail histopathology, which may be impractical. 5 Dermoscopy, often referred to as the 'dermatologist's stethoscope,' serves as a valuable tool that complements the limitations of naked-eye diagnosis, enhancing diagnostic accuracy. 6,7 Despite this, there is a paucity of literature on the dermoscopic characteristics of OM in psoriatics.…”

“…The advent of IL‐17‐related biologics has been associated with an increased incidence and progression of toenail OM, necessitating timely and accurate clinical assessment and intervention to prevent OM exacerbation. However, achieving a definitive diagnosis often faces challenges, as it requires direct fungal examination, culture or nail histopathology, which may be impractical 5 …”