Background Onychomycosis is multifactorial in origin. Studies have suggested an autosomal dominant pattern of inheritance and human leukocyte antigen DR4 (HLA-DR4) has been shown to protect against onychomycosis in an Ashkenazi Jewish population.
Aim This study investigates HLA class II association in a Mexican Mestizo population with Trichophyton rubrum onychomycosis.
Methods This was a prospective case–control study. Mexican Mestizos with a clinical diagnosis of onychomycosis and culture positive for T. rubrum were recruited, together with age- and sex-matched controls. First-degree relatives were also investigated for onychomycosis. Case–control samples were HLA typed by polymerase chain reaction sequence-specific primer based analysis.
Results Twenty-one cases and 42 controls were recruited with a mean age of 40 years (range: 18–58 years). HLA-DR6 was found in seven (33%) cases and 19 (45%) controls [P < 0.023, odds ratio (OR) = 0.088, 95% confidence interval (CI): 0.01–0.71]. Six (29%) cases and three (7%) controls had an affected child (P < 0.043, OR = 9.15, 95% CI: 1.07–78.31), and 13 (62%) cases and 12 (29%) controls had an affected first-degree relative (P < 0.02, OR = 4.0, 95% CI: 1.1–14.3).
Conclusions These results suggest that HLA-DR6 confers protection against the development of onychomycosis in a Mexican Mestizo population. Having an affected first-degree relative significantly increases the risk of onychomycosis, suggesting genetic susceptibility.