In the present study, we reported, to the best of our knowledge, the first Brazilian case of CMMRD associated with a biallelic loss of MSH6 in a child who developed two metachronous brain tumors, an anaplastic TP53‐mutant SHH medulloblastoma at 6 years of age and a dpHGG, H3 wild type, and IDH wild type (dpHGG) ~4 years later. Here, MSH6 is linked to medulloblastoma.