Pheochromocytomas and
paragangliomas are
neuroendocrine tumors which arise from adrenal medulla, and sympathetic or parasympathetic nerves, respectively. Hereditary cases afflicted by both or either
pheochromocytomas and
paragangliomas have been reported: these are called hereditary
pheochromocytoma/
paraganglioma syndromes (
HPPS). Many cases of
HPPS are caused by mutations of one of the
succinate dehydrogenase (SDH) genes; mainly SDHB and SDHD that encode subunits for the mitochondrial respiratory chain complex II. In this study, we investigated mutations of SDH genes in six
HPPS patients from four Japanese pedigrees using peripheral blood lymphocytes (from one patient with
pheochromocytoma and five patients with neck
paraganglioma) and
tumor tissues (from two patients with
paraganglioma). Results showed that all of these pedigrees harbor germline mutations in one of the SDH genes. In two pedigrees, a novel IVS2-2A>C mutation in SDHB, at the acceptor-site in intron 2, was found, and the
tumor RNA of the patient clearly showed frameshift caused by exon skipping. Each of the remaining two pedigrees harbors a reported missense mutation, R242H in SDHB or G106D in SDHD. Importantly, all these mutations are heterozygous in constitutional DNAs, and two-hit mutations were evident in
tumor DNAs. We thus conclude that the newly identified IVS2-2A>C mutation in SDHB is responsible for
HPPS. The novel mutation revealed by our study may contribute to improvement of clinical management for patients with
HPPS.