R46Q mutation in the succinate dehydrogenase B gene (SDHB) in a Japanese family with both abdominal and thoracic paraganglioma following metastasis.

Recently, nuclear genes encoding two mitochondrial complex II subunit proteins, SDHD and SDHB, have been found to be associated with the development of familial pheochromocytomas and paragangliomas (hereditary pheochromocytoma/paraganglioma syndrome: HPPS). Growing evidence suggests that a mutation of SDHB is highly associated with abdominal (or thoracic) paraganglioma and the following distant metastasis (malignant paraganglioma). Previously, we identified a novel heterozygous G to A point mutation at the first base of intron 3 of the SDHB gene (IVS3+1G>A) in a malignant abdominal paraganglioma from a Japanese patient. In the present study, we report another case of SDHB mutation (R46Q) in a Japanese patient with both abdominal and thoracic paraganglioma following malignant metastasis. In addition, we identified an asymptomatic carrier of SDHB mutation in this family. Our report highlights the pathogenic role of the SDHB mutation (R46Q) in malignant paraganglioma. We also discuss the desired protocol that should be adopted to follow up an asymptomatic carrier of this mutation.