Editor,

I read the recent paper by Choi et al. [1] with a great interest. Coto-Segura et al. [2] concluded that “The APOE-epsilon4 allele could be a risk factor for developing a severe form of psoriasis.” Indeed, the correlation between APOE-epsilon4 allele and medical disorder is widely studied. The report by Coto-Segura et al. seems to be a pioneer piece of work in dermatology on psoriasis. However, there are some points on the studies by Coto-Segura et al. to be concerned. First, although the number of cases and controls in this study seems statistically appropriate, the actual prevalence of a polymorphism might need more subjects, thousands of included cases, for verification. This is an important basic error in genome wide association case/control studies [5]. Second, the race and ethnic effect of the subjects is another point to be concerned for making a conclusion of the finding. The difference of APOE-epsilon4 allele distributions among different populations is confirmed in medical literature and this might lead to difference in its relationship to specific medical disorders. The good examples are those controversial reports on Alzheimer’s disease [1, 3, 4]. These points need clarification to strengthen the conclusion of the work.