Approximately 20% of patients diagnosed with a phaeochromocytoma or paraganglioma carry a germline mutation in one of the succinate dehydrogenase (SDHx) genes (SDHA, SDHB, SDHC and SDHD), which encode the four subunits of the SDH enzyme. When a pathogenic SDHx mutation is identified in an affected patient, genetic counselling is proposed for first-degree relatives. Optimal initial evaluation and follow-up of people who are asymptomatic but might carry SDHx mutations have not yet been agreed. Thus, we established an international consensus algorithm of clinical, biochemical and imaging screening at diagnosis and during surveillance for both adults and children. An international panel of 29 experts from 12 countries was assembled, and the Delphi method was used to reach a consensus on 41 statements. This Consensus Statement covers a range of topics, including age of first genetic testing, appropriate biochemical and imaging tests for initial tumour screening and follow-up, screening for rare SDHx-related tumours and management of elderly people who have an SDHx mutation. This Consensus Statement focuses on the management of asymptomatic SDHx mutation carriers and provides clinicians with much-needed guidance. The standardization of practice will enable prospective studies in the near future.

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Renal transplantation has important benefits in people with end-stage renal disease, with improvements in mortality, morbidity and quality of life. Whilst significant advances in transplantation techniques and immunosuppressive regimens have led to improvements in short-term outcomes, longer-term outcomes have not improved dramatically. New-onset diabetes after transplantation appears to be a major factor in morbidity and cardiovascular mortality in renal transplant recipients. The diagnosis of new-onset diabetes after renal transplantation has been hampered by a lack of clarity over diagnostic tests in early studies, although the use of the WHO criteria is now generally accepted. HbA1c may be useful diagnostically, but should probably be avoided in the first 3 months after transplantation. The pathogenesis of new-onset diabetes after renal transplantation is likely to be related to standard pathogenic factors in Type 2 diabetes (e.g. insulin resistance, β-cell failure, inflammation and genetic factors) as well as other factors, such as hepatitis C infection, and could be exacerbated by the use of immunosuppression (glucocorticoids and calcineurin inhibitors). Pre-transplant risk scores may help identify those people at risk of new-onset diabetes after renal transplantation. There are no randomized trials of treatment of new-onset diabetes after renal transplantation to determine whether intensive glucose control has an impact on cardiovascular or renal morbidity, therefore, treatment is guided by guidelines used in non-transplant diabetes. Many areas of uncertainty in the pathogenesis, diagnosis and management of new-onset diabetes after renal transplantation require further research.

Objective: With the discovery that familial phaeochromocytoma and paraganglioma syndrome can be caused by mutations in each subunit of the succinate dehydrogenase enzyme (SDH), has come the recognition that mutations in the individual subunits have their own distinct natural histories. Increased genetic screening is leading to the identification of increasing numbers of, mostly asymptomatic, gene mutation carriers and the implementation of screening strategies for these individuals. Yet there is, to date, no international consensus regarding screening strategies for asymptomatic carriers.Design: A comprehensive PubMed search from 1/1/2000 to 28/2/2018 was undertaken using multiple search terms and subsequently a manual review of references in identified papers to identify all clinically relevant cases and cohorts. In this review, the accumulated, published experience of phenotype and malignancy risks of individual SDH subunits is analysed. Where possible screening results for asymptomatic SDH mutation carriers have been analysed separately to define the penetrance in asymptomatic carriers (asymptomatic penetrance). Results:The combined data confirms that "asymptomatic penetrance" is highest for SDHD and when there is penetrance, the most likely site to develop a PGL is head and neck (SDHD) and extra-adrenal abdominal (SDHB). However, the risk in SDHB carriers of developing HNPGL is also high (35.5%) and a PCC is low (15.1%), and in SDHD carriers there is a high risk of developing a PCC (35.8%) or abdominal PGL (9.4%) and a small, but significant risk at other sympathetic sites. The data suggest that the risk of malignant transformation is the same for both PCC and extra-adrenal abdominal PGLs (30%-35%) in SDHB carriers. In SDHD carriers, the risk of malignant transformation was highest in HNPGLs (7.5%) and similar for sympathetic sites (3.8%-5.2%). Conclusions:Using this data, we suggest surveillance screening of asymptomatic carriers can be tailored to the underlying SDH subunit and review possible surveillance programmes. K E Y W O R D S imaging, MRI, paraganglioma, phaeochromocytoma, screening, SDH, succinate dehydrogenase, surveillance S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section at the end of the article. How to cite this article: Tufton N, Sahdev A, Drake WM, Akker SA. Can subunit-specific phenotypes guide surveillance imaging decisions in asymptomatic SDH mutation carriers?. Clin Endocrinol. 2019;90:31-46. https://doi.