A prospective observational study of pigmented naevi changes in psoriasis patients on biologic therapy.

Background/objectives: Patients on biologic therapy are thought to be at increased risk of developing non-melanoma skin cancers and melanomas. It is unknown whether biologic therapy alters the natural history of melanocytic naevi. Therefore, a prospective observational study was conducted to determine whether psoriasis patients on biologic therapy develop changes in naevi.

Methods: Clinical and dermoscopic assessment of all melanocytic naevi was performed in 45 psoriasis patients on biologic therapy versus a control cohort of 43 subjects, using sequential digital dermoscopic imaging and total body photography. The mean follow-up period was 1.5 years.

Results: The study and control patients had comparable age, gender, previous and family history of non-melanoma skin cancers and melanomas, as well as previous sun exposure and total number of naevi. The number of naevi with major dermoscopic changes was 3% in the study and 1.9% in the control group, with an adjusted incidence rate ratio of 1.45 (95% confidence interval 0.90-2.33; P = 0.125). The rate of minor changes was 15.9% in the study group versus 19.4% in the control (adjusted incidence rate ratio 0.77, 95% confidence interval 0.57-1.08; P = 0.14). There were six new dysplastic naevi in 4/45 biologic patients and four in 4/43 controls; however, the difference was not significant (relative risk 0.96, 95% confidence interval -0.12 to 0.12; P = 0.95). There were no melanomas in either group.

Conclusion: Over a mean follow-up period of 1.5 years there was no evidence of significantly different changes in naevi or development of new dysplastic naevi in psoriasis patients on biologic treatment compared to controls.