Association between onychodystrophy and human T-lymphotropic virus type 1 infection

Objective: To assess the association between human T-lymphotropic virus type 1 (HTLV-1) infection and onychodystrophy. Methods: This was a cross-sectional study. At our institute, we provide HTLV-1 testing to relatives of HTLV-1-infected people and patients with suspected HTLV-1-associated diseases. The diagnosis of onychodystrophy was made clinically before testing for HTLV-1; the number and distribution of affected nails was registered. We assessed the association between onychodystrophy and HTLV-1 through bi- and multivariable analyses. Logistic regression was used to adjust for age, sex, and indication for HTLV-1 testing, using six affected nails (90^th percentile) as the cut-off point. Results: Between April 2006 and March 2008, we included 893 subjects; their mean age was 38 years (standard deviation 19 years), and 527 (59%) were women. Onychodystrophy of one or more nails was observed in 323 participants (36%), and 236 subjects (26%) were HTLV-1-positive. The median number of affected nails was higher in HTLV-1-positive than in HTLV-1-negative subjects (Mann-Whitney test, p < 0.001). Thirty-eight of 97 subjects with six or more affected nails (39%) were HTLV-1-infected, compared to 198 of 796 subjects with fewer than six affected nails (25%) (crude OR 1.9, 95% confidence interval (CI) 1.2-3.1; p = 0.003). This association remained significant in the multiple logistic regression model (adjusted OR 2.0, 95% CI 1.2-3.3; p = 0.005). Conclusions: There is an independent association between HTLV-1 infection and onychodystrophy. Patients with an HTLV-1 infection might have a higher risk for onychomycosis given the abnormal nail plate and a decreased T-cell-mediated immunologic response.