MDH2 and neurofibromatosis type 1: Herein we describe two NF1 patients with multiple tumours harboring dual mutations, which, in addition to the previously reported patients carrying SDHD/NF1 mutations, suggest that the co-occurrence of NF1 mutations with variants affecting other PPGL susceptibility genes (i.e. DLST, MDH2, SDHD), or still unknown genes, could be responsible of this unusual clinical manifestation in some NF1 patients.