The prevalence, aetiological agents and therapy of onychomycosis in patients with psoriasis:: a prospective controlled trial

Background. Nail involvement morphologically resembling onychomycosis frequently accompanies psoriatic lesions. The role of psoriasis as a predisposing factor for onychomycosis and the possible influence of psoriasis on responsiveness of onychomycosis to treatment are controversial. Aim. To investigate the frequency of onychomycosis, the aetiological agents responsible for it, and the efficacy of terbinafine 250 mg/day in patients with psoriasis compared with controls in order to reveal the role of psoriatic process on fungal growth. Methods. Over a 1-year period, 168 patients with psoriasis and 164 nonpsoriatic controls were recruited. In the case of clinically suspected of fungal infection, further mycological investigations were performed. Systemic terbinafine therapy 250 mg daily for 12 weeks was administered to the patients with onychomycosis. Patients were followed up clinically and mycologically for 24 weeks. Results. Onychomycosis was diagnosed in 22 patients with psoriasis (13.1% of the psoriasis group, which constituted 28.6% of patients with suspicion of onychomycosis) and 13 controls (7.9% of control group; 40.6% of controls with suspicion of onychomycosis). The prevalence rates of onychomycosis were similar in both groups. The most commonly isolated fungi were dermatophytes in the psoriasis group and nondermatophytic moulds in controls. Dermatophytes were more common in psoriatic than control nails (P = 0.02). All patients in each group were cured at the end of the therapy. Conclusion. It seems that nail psoriasis constitutes a risk factor not for onychomycosis, but specifically for dermatophytic nail infections. Because of the similar therapeutic results in each group, different antifungal treatment protocols may not be needed in psoriasis. However, to confirm this, new comprehensive studies are necessary.