A Mycological Study of Onychomycosis

Moon, Kee Chan; Cho, Baik Kee

Abstract

For the sake of simplicity, it is as well to divide nail pathogens into dermatophytes (moulds) and yeasts. Most dermatophyte infections of nails, some over 80% are caused by Trichophyton rubrum (T. rubrum), with Trichophyton mentagrophytes (T. mentagrophytes) found in around 10% of cases. Occasionally there are mixed or pure infections with yeast mostly Candida albicans. Rarely nondermatophytic fungi such as Scopolariopsis, Aspergillus, Scytalidium and Fusarium species are found to be causative agents in onychomycosis. Importance of accurate diagnosis of onychomycosis has been increasing because more than half of the patients with nail disorders are non-onychomycotic. Direct smear with KOH is the most simple and valuable laboratory test which will takes about 20 to 30 minutes. the positive rate of direct smear is relatively high (40~60%), but permanent keeping of the positive microscopic findings is not possible. Fungus culture is the most essential laboratory test for identifying the species of the causative fungi even though the positive rate is low (20~50%) and takes 3 to 4 week to have the result. Histopathologic test is a non-invasive diagnostic method with high positive rate (70~90%). The test is very helpful for confirming the mixed infection of the onychomycosis. KONCPA test abbreviated by "melting with KOH of the nail clippings and PAS staining" is a new diagnostic method. Though the test requires some skill and equipments, the positive rate is high (70~90%) and permanent keeping of the positive findings is possible.