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We have read with great interest the recent article by Tufton and coworkers reporting on the risk of metastasis in patients with paraganglioma (PGL) tumours associated with germline SDHA mutations (Tufton et al. 2017). Herein, we report a further case of a malignant PGL in a 46-year-old man with a succinate dehydrogenase complex flavoprotein subunit A (SDHA) germline mutation (c.91C > T, p.Arg31*). In the case we describe, following the initial surgical removal of a left-sided retroperitoneal PGL, twenty-three years elapsed before the development of a bony metastasis in the eighth left rib. This observation is similar to that of Tufton and coworkers who reported two patients, who developed metastatic disease in 16 and 37 years, respectively, following initial diagnosis (Tufton et al. 2017). During investigations for this case, we found that the rib metastasis was avid on 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) computed tomography (CT), but not avid on radiolabeled I131 metaiodobenzylguanidine (MIBG) imaging (Fig. 1). This observation of SDHA-related malignant PGL is in keeping with SDHBand SDHD-associated PGL, in which reduced avidity on MIBG imaging is due to reduced tumoural expression of noradrenaline transporters (Timmers et al. 2007). This clinical report supports the recent literature that suggests a risk of malignancy in patients with SDHA mutated PGL (Bausch et al. 2017, Casey et al. 2017, Tufton et al. 2017). The prolonged time interval between diagnosis and development of metastases in our case suggests that SDHA-related tumours are slow growing but it does support long-term surveillance programmes for patients with germline SDHA mutations. Although mutations in SDHB, SDHC and SDHD gene subunits were first identified as predisposition genes for the development of phaeochromocytoma (PC) and PGL tumours over 15 years ago, SDHA was first associated with PGL only seven years ago (Burnichon et al. 2010) and, more recently, with wild-type gastrointestinal stromal tumours (WT GIST) (Evenepoel et al. 2015). It is now recognised that the SDHA gene is the most common SDHx germline mutation implicated in development of SDH-deficient WT GIST (Boikos et al. 2016). Recently, the European-AmericanAsian Pheochromocytoma-Paraganglioma Registry Study Group reported on 34 index cases with germline SDHA mutations and PC or PGL tumours. This group described a high prevalence of head and neck PGL in the SDHA cohort 15/34 (44%) and metastatic disease was reported in 4/34 (12%) (Bausch et al. 2017). Here, we report the case of a 46-year-old man who first presented at age 23 years with headache, heat intolerance and abdominal pain. He was subsequently diagnosed with a left-sided retroperitoneal paragangliomama, which was surgically resected. The man had no family history of endocrine tumours and no additional relevant medical history. Following surgery, the patient was surveyed in primary care with annual urinary metanephrine testing. Twenty-three years later he was referred to our specialist neuroendocrine tumour service at Cambridge University Hospital NHS Foundation Trust, due to an elevated urinary normetanpehrine level (urinary normetanephrine 5870 nmol/24 h, reference range 0–4900; urinary metanephrine 756 nmol/24 h, reference range 0–2000), which was first observed 3 months earlier. On review, the patient denied symptoms suggestive of catecholamine excess and, importantly, denied any of the symptoms that he reported at the time of his initial presentation. Review of systems revealed that his only complaint was left side rib pain. Previous investigations in primary care included a plain chest radiograph which did not reveal any abnormality. We performed plasma metanephrine testing and found an elevated normetanephrine level (2864 pmol/L, reference range <1000 pmol/L) in the context of normal plasma metanephrine (197 pmol/L, reference range <600 pmol/L) and methoxytyramine measurements (95.6 pmol/L, reference range <180 pmol/L). In light of the elevated normetanephrine level in urine and plasma, CT of the

A case of a metastatic SDHA mutated paraganglioma re-presenting twenty-three years after initial surgery