The article discusses the factors involved in psoriasis development and exacerbations, being grouped as intrinsic and extrinsic factors. Psoriasis has an important impact on patients’ quality of life, the patients often experience depression, anxiety and stigma. Psoriasis is one of the most common dermatological diseases, however, its pathogenesis is still incompletely elucidated. I consider that this review represents a valuable work given that the authors offer a detailed discussion about the risk factors involved in psoriasis onset and course. The knowledge of these factors may improve the management of the disease.

There are no major points in the article that need clarification. The abstract is well written and the authors present clearly the aim of the manuscript. The title is adequately chosen. I consider that the article is thoroughly documented and the references are relevant and recent. The introduction is well structured. The authors underline that the pathogenesis of psoriasis is complex and based on the interplay between intrinsic and extrinsic factors. Figure 1 summarizes very well the subject of the manuscript.

The article by Kamiya et. al is a non-systematic review, however it is very well structured in section and subsection; the article is easy to read. The authors selected a high number of articles that they discussed in the manuscript.

The factors that are involved in psoriasis pathogenesis are well established. However, I consider that the article brings an updated perspective, that can help the dermatologist improve the management of his patients.

The conclusions of the article are consistent with its content. Factors such as obesity, dyslipidemia, hypertension should be kept in mind; the association between psoriasis and metabolic syndrome should always be considered. Certainly, the pathogenesis of psoriasis is not yet completely elucidated, therefore every detail must be very well analyzed. The conclusions answer the aims of the manuscript and are supported by references.

I consider that the article fits the aim and scope of the journal and represents an important contribution in the field.