Higher CHEK2 and JAK2 expression have been correlated with better survival among patients with rectal adenocarcinoma, lung squamous cell carcinoma, breast cancer, ovarian cancer and several other cancer types. It has been suggested that genome alterations due to lowered or loss of CHEK2 and JAK2 expression may exacerbate cancer progression and predict poor patient survival. In this report, we present the clinical case of a 35-year-old patient exhibiting multiple tumours, an aggressive course, whose genetic analysis revealed a germinal mutation in CHEK2 gen, somatic JAK2V617F and a germinal novel variant in Adenomatous Polyposis Coli (APC) gene of uncertain significance may account for the polyposis and medulloblastoma in the patient, given the variant's genomic location. It is also possible that two germline mutations (CHEK2 and APC) are causing two concurrent conditions in the patient with poorer clinical course.