First, the proband had no pathogenic variant in NF1, IDH1, IDH2, FH, MDH2 or SLC25A11 which predispose to familial PCC/PGL nor in a group of 30 cancer-predisposing genes (22), that is, APC, ATM, BAP1, BARD1, BMPR1A, BRCA1, BRCA2, BRIP1, CDH1, CDKN2A, CDK4, CHEK2, EPCAM, GREM1, MITF, MLH1, MSH2, MSH6, MUTYH, NBN, PALB2, PMS2, POLD1, POLE, PTEN, RAD51C, RAD51B, SMAD4, STK11 and TP53. Thus, we decided to focus on the nucleotide variants which were present in the germline of III-1 but absent in II-2 in agreement with our working hypothesis. Here, IDH1 is linked to cancer.