A case of juvenile-onset pheochromocytoma with KIF1B p.V1529M germline mutation.

In 2008, a familial noradrenergic pheochromocytoma (PCC) with a KIF1B germline mutation in exon 41 was reported in a 24-year-old female proband and her family. However, in 2020, the same research group reported that the cause of PCC in this family was a MAX germline mutation and was not due to the KIF1B mutation. In this study, we investigated the pathogenicity of a KIF1B germline mutation detected in a 26-year-old woman with juvenile-onset noradrenergic PCC. She was surgically treated and did not have a family history of PCC. We performed whole-exome sequencing, Sanger sequencing, and immunohistochemical and gene expression analyses of catecholamine-synthesizing enzymes. Three tumors with associated somatic mutations were used as the control group. Whole-exome sequencing revealed a p.V1529M KIF1B germline mutation in exon 41 in our patient, and no other associated germline and somatic mutations, including MAX, were detected. Sanger sequencing confirmed the presence of both mutant and wild-type alleles in the tumor. Among the catecholamine-synthesizing enzymes, the expression of phenylethanolamine-N-methyl transferase was suppressed. An in silico analysis of the p.V1529M mutation showed a score suggestive of pathogenicity. After evaluation with the international guideline for sequence variants, p.V1529M mutation was still classified as a variant with uncertain significance; however, our data, including the in silico analysis data, provided certain evidences that met the criteria supporting its pathogenicity. Therefore, this study can support future studies in proving the pathogenicity of the KIF1B p.V1529M mutation.