Objective The results of register studies suggest an association between Parkinson's disease (PD) and melanoma. We studied the frequency and profile of early markers of PD in patients with malignant melanoma.

Methods 100 participants were enrolled in a prospective observational study, of whom 65 had a history of high-risk cutaneous (n=53) or uveal (n=12) melanoma (31 women; age, 61.2±14.9 years) and another 35 served as control participants (19 women; 54.6±20.5 years). Participants underwent assessments of motor function (Unified PD Rating Scale; keyboard tapping test), olfactory function, colour vision, depressive symptoms, the Non-Motor Symptoms Questionnaire, and transcranial brain sonography. Raters were blinded to the diagnosis and clinical data of study participants.

Results Patients with melanoma showed increased frequency of substantia nigra hyperechogenicity and prodromal motor and non-motor features of PD, especially asymmetric motor slowing and apathy. Hyposmia and colour vision disturbance were, however, infrequent. Larger echogenicity of substantia nigra correlated with lower serum iron in patients with melanoma, similar to previously reported findings in PD, and independently from the earlier findings, with lighter skin pigmentation. Substantia nigra hyperechogenicity, combined with motor asymmetry or hyposmia, was present at baseline in all participants with mild or definite parkinsonism diagnosed after 1 year. Parkinsonism was specifically related to melanoma location at the sun-exposed skin of the head or neck.

Conclusions History of melanoma was associated with increased prevalence of prodromal markers of PD. Their predictive value needs to be established in long-term investigations. The similarity of serum iron characteristics found in patients with melanoma and PD deserves further research.