Onychomycosis in systemic lupus erythematosus: a case control study

OBJECTIVE: Immunosuppressed patients are prone to develop onychomycosis. In systemic lupus erythematosus (SLE) there are no previous studies. We aimed to establish the prevalence, clinical characteristics, and organisms causing onychomycosis in SLE patients compared with controls. METHODS: Fifty consecutive patients with SLE seen on an outpatient basis and 50 sex and age matched controls. Samples were obtained when abnormal nails were found: distal and lateral subungual onychomycosis (DLSO), white superficial, proximal subungual (PSO), endonyx, and total dystrophic (TDO). The nail specimens were evaluated in a blinded fashion, by mycologic examination and culture. RESULTS: Of the SLE patients, there were 12 (24%) with onychomycosis confirmed. The distribution of the clinical forms were TDO 6/12 (50%), DLSO 4/12 (33%), and PSO 2/12 (17%). The causative organisms were isolated in 6 cases: Trichophyton rubrum 3/6 (50%), Trichophyton mentagrophytes 2/6 (33%), Microsporum canis 1/6 (17%). Direct microscopy examination revealed fungal elements in the other 6 cases. Of the 50 controls, 4 (8%) presented onychomycosis [p = 0.029; OR 3.63 (95% CI 1.04-14.68)]: DLSO 2/4 (50%), and TDO 2/4 (50%). Trichophyton rubrum was isolated in 1 and Trichophyton mentagrophytes in 1 (50%). CONCLUSION: These data suggest a higher prevalence of onychomycosis in SLE versus controls, the predominant organism was Trichophyton rubrum, an anthropophilic dermatophyte. Toenails were more frequently affected and the most common clinical presentation was TDO. PSO, a rare pattern in immunocompetent subjects, was exclusively found in the lupus group.