Recent studies have shown activating mutations in NRAS, KRAS, and BRAF in MM, making the MAPK pathway a significant therapeutic target also in MM.3-5 A retrospective study has demonstrated clinical activity of trametinib in patients with MM with RAS-mutated tumors.14 Eleven of 21 evaluable patients in our study received trametinib, either alone or in combination with other drugs. Here, NRAS is linked to Miyoshi myopathy.