Background Congenital melanocytic naevi (CMNs) can be associated with abnormalities of the cental nervous system (CNS) and/or with melanoma. Quoted incidences for these complications vary in the literature, as do recommendations for investigations and follow-up.
Objectives To determine the incidence of complications, and to identify phenotypic features associated with a higher risk of complications.
Methods We reviewed records of 224 patients with CMNs seen in Dermatology clinic between 1991 and 2007. Patients were excluded if they had a complication at the time of referral. Magnetic resonance imaging (MRI) of the CNS was offered on the basis of CMN phenotype. Follow up was in clinic and/or by postal questionnaires.
Results One hundred and twenty patients (54 boys and 66 girls) who had MRI of the CNS were included in the analysis. Mean age at MRI was 2·46 years (median 1·20). Mean follow up was 8·35 years (median 7·86). Sixty-five per cent had naevi > 20 cm projected adult size or multiple CMNs (40% > 40 cm), and 83% had satellite lesions at birth. Outcome measures were MRI abnormality, clinical neurological abnormality, any tumour, malignant melanoma, and death. No complications were seen in the 16 patients with no satellite lesions at birth. MRI and/or clinical neurological abnormalities were found in 22 patients (18%) and were significantly associated with projected adult size of the CMN (particularly > 40 cm), and independently with male gender. Tumours occurred in five patients, two of which were malignant melanoma (1·7%). Due to small numbers there was no significant association between phenotype and occurrence of tumours. Three patients (2·5%) died (one from neuromelanosis and two from melanoma in patients with normal MRI scans). Death was significantly associated with CMN size > 40 cm. Importantly, there was no significant association between CMN distribution (including posterior axial location) and adverse outcomes.
Conclusions This is the largest study of CNS imaging in patients with CMNs. We report a newly recognized association between male gender and neurological complications, dispute the previously reported association between CMN site and neurological complications, and quantify the associations between CMN size, satellite lesions and neurological complications. We make recommendations for the management of these patients.