Psoriasis and melanocytic naevi: does the first confer a protective role against melanocyte progression to naevi?

Some of the cytokines that have effects on melanogenesis are also reported to be involved in psoriasis.

We therefore studied the relationship between psoriasis and melanocytic naevi. In particular, the aim of our study was to investigate the number of melanocytic naevi in patients with psoriasis vs. controls.

We performed a prospective case-control study, analysing 93 adult patients with psoriasis and 174 adult aged-matched controls. For each participant a questionnaire was completed to establish personal data, personal medical history, and personal and familial history of skin cancer and psoriasis. We analysed interleukin (IL)-1α, IL-6 and tumour necrosis factor (TNF)-α gene expression at the peripheral blood mononuclear cell level in patients with psoriasis and in controls.

In our study, patients with psoriasis presented a lower number of areas with naevi in comparison with controls (P < 0·0001). Nobody had ever had squamous cell carcinoma or melanoma in the psoriatic group; moreover, there was a significant difference in familial history of melanoma between the two groups (none in the psoriatic group vs. 8% in the control group; P < 0·05). IL-1α, IL-6 and TNF-α expression levels were higher in patients with psoriasis.

People with psoriasis had fewer melanocytic naevi. This suggests that the proinflammatory cytokine network in psoriasis skin might inhibit melanogenesis, melanocyte growth and/or progression to naevi.