Congenital Melanocytic Nevus Syndrome: A Case Series.

Congenital melanocytic nevus syndrome (CMNS) is the result of an abnormal proliferation of melanocytes in the skin and central nervous system caused by progenitor-cell mutations during embryonic development. Mutations in the NRAS gene have been detected in many of these cells. We present 5 cases of giant congenital melanocytic nevus, 3 of them associated with CMNS; NRAS gene mutation was studied in these 3 patients. Until a few years ago, surgery was the treatment of choice, but the results have proved unsatisfactory because aggressive interventions do not improve cosmetic appearance and only minimally reduce the risk of malignant change. In 2013, trametinib was approved for use in advanced melanoma associated with NRAS mutations. This drug, which acts on the intracellular RAS/RAF/MEK/pERK/MAPK cascade, could be useful in pediatric patients with CMNS. A better understanding of this disease will facilitate the development of new strategies.