De novo SDHB gene mutation in a family with extra-adrenal paraganglioma.

A 14-year-old male presented with abdominal pain. Imaging illustrated a left-sided adrenal mass; he underwent a left nephrectomy, confirming an extra-adrenal PGL. Germline genetic testing revealed a heterozygous, likely pathogenic mutation in the SDHB gene. The patient's family subsequently underwent genetic testing; his mother and sister were both positive for the familial SDHB mutation. Cascade testing for the proband's maternal aunt and maternal grandparents was negative for the familial mutation. SNP genotyping was used to confirm relationships. This is the second reported case of a de novo SDHB gene mutation and the first reported case of a confirmed de novo mutation in a patient who was not the initial proband. As SDHB-associated PGLs and PCCs are expected to be more aggressive and malignant, it is imperative to identify patients with SDHB mutations early. Given that many patients with germline mutations have no family history of PGL of PCC, the possibility of de novo mutations must be considered. Further studies are needed to determine the rate of de novo mutation in SDHB and other SDH-complex genes. Up to 41% of patients with paragangliomas (PGL) or pheochromocytomas (PCC) have an identifiable hereditary cancer predisposition syndrome. Mutations in 12 genes are known to increase the risk of PGL and/or PCC; however, the de novo rate is mostly unknown. Only one case report exists of a de novo SDHB mutation. We present the second case of a family with a de novo SDHB mutation.