Abstract: Objective To study the prevalence of toenail onychomycosis in the patients with diabetes mellitus. Methods The incidence and predisposing factors of onychomycosis were studied in the in-and out-patients with diabetes mellitus(n=456). The data were also compared with non-diabetic patients (control group, n=350). Results The prevalence rates of toenail onychomycosis were 20.8% and 9.4% in the diabetics and control group, respectively, with statistical difference (P<0.001). In both groups, it was found that the prevalences were significantly correlated with the ageing and male gender (P<0.001). In the diabetic group the infection of dermatophytes and yeasts was 47.4% and 40.0%, respectively, but in the control group it was 68.5% and 25.7%, respectively. The single factor analysis demonstrated that the predisposing factors for toenail onychomycosis included the duration of diabetes (P<0.001), the disturbance of peripheral circulation (P<0.05), peripheral neuropathy (P<0.001), retinopathy (P<0.001) and oral immunosuppressive agents (P<0.001). Conclusions The prevalence rate of toenail onychomycosis is 2.2 times higher in diabetics than that in the controls. The predisposing factors include ageing, male, the duration of diabetes, the disturbance of peripheral circulation, peripheral neuropathy, retinopathy and oral immunosuppressive agents.

Key words: Diabetes mellitus, Onychomycosis, Prevalence, Disease susceptibility