Fungal nail infections: far more than an aesthetic problem

Unequivocal morphological diagnosis of fungi in morphologically abnormal nails

AIMS

To analyse the prevalence of fungi in abnormal nails by morphological diagnosis. Prevalence studies of onychomycoses in temperate climate zones have yielded widely varying rates, possibly reflecting the confounding effects of referral bias, sampling specificity and intrinsic sensitivity of the diagnostic techniques employed.

METHODS AND RESULTS

The method employed to identify fungi in nails entailed primary fixation using a non-formaldehyde-based coagulative fixative (BoonFix; Finetec, Japan) and microwave-enhanced processing to histology, followed by staining the paraffin sections with periodic acid-Schiff, using haematoxylin as a routine counterstain. The results of 990 nail samples were tabled for statistical analysis related to gender, patient age and diabetes mellitus status. In four of the 990 (< 1%) analysed cases the diagnosis was found to be equivocal using the method employed. These cases were jointly reviewed for definitive diagnosis. The overall prevalence of invasive hyphal structures was found to be 606/990 (approximately 61%). The relative risk for fungal infection in morphologically abnormal nails was found to be higher for persons < 20 years old or diabetic patients aged > or = 71 years.

CONCLUSIONS

The 61% positivity rate for fungi found justifies systematic direct submission of samples from abnormal nails for histological confirmation in order to avoid unwarranted treatment.

Onychomycosis in Taiwan

The pathogens of onychomycosis have implications in choosing therapy. We aimed to survey the pathogens of onychomycosis in Taiwan and further analyse the distribution of pathogens in various conditions. We also compared the distribution of pathogens in Taiwan with those in various countries. This study included 182 cases of onychomycosis who attended our clinic between January and December 2001. Histopathologic examination and fungus culture of the nail specimens were performed to confirm the diagnosis and identify the pathogens. The pathogens were dermatophytes in 101 patients (55.5%), Candida in 66 (36.3%), and non-dermatophyte moulds in 16 (8.2%). Candida was more frequently seen in patients older than 60 years (40.9%), females with fingernail onychomycosis (66.7%) or combined fingernail and toenail onychomycosis (58.3%), and presence of paronychia (57.9%). Dermatophytes are the predominant pathogens in temperate Western countries; meanwhile, Candida and non-dermatophyte moulds are prevailing in Mediterranean and tropical countries including Taiwan. Clinicians should appreciate that the pathogens of onychomycosis may vary in different patient groups and geographical locations, and choose optimal antifungal agents accordingly.