Myasthenia gravis induced by pembrolizumab in a patient with metastatic Merkel cell carcinoma

Until now, definite diagnosis of dermatophytic onychia has been made by taking a nail sample and placing it in culture. The result is usually obtained only after 2 to 3 weeks. More recently, diagnosis within a few minutes after sampling has become possible thanks to an immunochromatography technique developed in Japan and now available in France: the Diafactory Tinea Unguium® test strip (Biosynex, France).Over a 12-month period, 80 nail samples from 80 patients giving rise to a positive fungal culture were included in the study. For each patient, part of the removed nail was stored at room temperature and an immunochromatographic test was retrospectively performed according to the supplier's instructions. A small fragment of nail (≥ 1 mg) was mixed with a few drops of reagent in a tube for 1 min and the test strip was then placed in the tube with the result being visible to the naked eye (control strip, positivity strip) after incubation for a few minutes.Compared with the culture method used for 51 isolated dermatophytes (42 Trichophyton rubrum, 9 Trichophyton interdigitale), the sensitivity of the rapid test was 96.07% (49/51). For the 29 other fungal cultures (10 Fusarium sp., 3 Scytalidium sp., 3 Scopulariopsis brevicaulis,3 Aspergillus sp., 1 Alternaria sp., 3 Candida albicans, 1 Candida parapsilosis, 1 Trichosporons sp., 1 Rhodotorula sp., and 3 Corynebacterium sp.), the specificity was 75.86% (22/29). False positives were mainly due to the genera Fusarium and Scopulariopsis (6 of 7 false positives), which were the likely cause of onychomycosis.This rapid test could be useful in limiting excessive clinical diagnosis of dermatophyte onychomycosis. The rapid test has several advantages: ease of application, speed of results, and good performance, which, together, could improve diagnostic certainty during the actual consultation, thus limiting prolonged unnecessary prescriptions of antifungal treatments, while waiting for the laboratory culture results (3 weeks for a negative result).