ACVR1 and diffuse intrinsic pontine glioma: It is note worthy that some somatic recurrent constitutively activating mutations in the ACVR1/ALK2 gene (namely R258G, R206H, G356D, and G328E/V/W), previously described in FOP patients, have been reported in 21% of diffuse intrinsic pontine glioma (DIPG) samples [28,29].