Screening for Hereditary Hemochromatosis in Newly Referred Diabetes Mellitus.

Aims: Hereditary hemochromatosis (HH) is the most common inherited disease in European populations. It is particularly common in people of Irish heritage, approximately 2% of whom will be at risk of iron overload as a result of human homoeostatic iron regulator protein (HFE) gene mutations. We aimed to evaluate the utility of screening for HH in newly referred patients with DM of Irish heritage in a prospective study. Methods: Of 575 patients newly referred between March 2018 and March 2021, 556 attended for blood testing, to include fasting transferrin saturations, prior to their first clinic visit. Patients with elevated transferrin saturations were further screened for hereditary hemochromatosis (HH) with HFE gene analysis. Results: Transferrin saturations were elevated in 13 of 556 patients (2.3%), 3 of whom had a preexisting diagnosis of HH. Of the remaining 10 patients, 7 had HFE gene mutations suggestive of HH (2 C282Y homozygous, 3 C282Y/H63D compound heterozygous, and 2 H63D homozygous), 1 was a HH carrier (C282Y heterozygous), and 2 had normal genetics. Conclusions: The prevalence of HH of 1.8% in this screened DM population is lower than the reported incidence of HH in the Irish population, suggesting a limited utility of routine screening for HH in newly referred patients with DM.

A review of the tumour spectrum of germline succinate dehydrogenase gene mutations: Beyond phaeochromocytoma and paraganglioma.

The citric acid cycle, also known as the Krebs cycle, plays an integral role in cellular metabolism and aerobic respiration. Mutations in genes encoding the citric acid cycle enzymes succinate dehydrogenase, fumarate hydratase and malate dehydrogenase all predispose to hereditary tumour syndromes. The succinate dehydrogenase enzyme complex (SDH) couples the oxidation of succinate to fumarate in the citric acid cycle and the reduction of ubiquinone to ubiquinol in the electron transport chain. A loss of function in the succinate dehydrogenase (SDH) enzyme complex is most commonly caused by an inherited mutation in one of the four SDHx genes (SDHA, SDHB, SDHC and SDHD). This mechanism was first implicated in familial phaeochromocytoma and paraganglioma. However, over the past two decades the spectrum of tumours associated with SDH deficiency has been extended to include gastrointestinal stromal tumours (GIST), renal cell carcinoma (RCC) and pituitary adenomas. The aim of this review is to describe the extended tumour spectrum associated with SDHx gene mutations and to consider how functional tests may help to establish the role of SDHx mutations in new or unexpected tumour phenotypes.