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      Misleading localization by 18F-fluorocholine PET/CT in familial hypocalciuric hypercalcemia type-3: a case report

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          Abstract

          Background

          Familial hypocalciuric hypercalcemia (FHH) is a heterogeneous autosomal-dominant disorder of calcium hemostasis that may be difficult to distinguish clinically from mild primary hyperparathyroidism. Loss-of-function mutations mainly involving Arg15 residue of the adaptor-related protein complex 2, sigma subunit 1 (AP2S1) cause a rarer, more recently recognized form of FHH, FFH type-3. Recently, 18F-fluorocholine positron emission tomography/computed tomography (FCH-PET/CT) showed superior sensitivity to conventional imaging in localizing parathyroid adenomas. We report a new FFH type-3 patient who underwent unnecessary parathyroidectomy in association with misleading FCH-PET/CT imaging.

          Case presentation

          A 29-year old woman was initially evaluated for parathyroid hormone (PTH)-dependent hypercalcemia in 2013. Medical history was positive only for chronic constipation and malaise with no personal or family history of hypercalcemia, kidney stones, or neck surgery. Over seven years, serum calcium level was 2.51–2.89 mmol/L with concomitant PTH level of 58.7–94.8 mmol/L. Serum phosphate levels were in the low/low normal range. Serum creatinine and magnesium levels were normal. 25-hydroxy vitamin D level was 13 nmol/L. 24-hour urine calcium level was 1.92 mmol/day but increased to 6.99 mmol/day after treatment with cholecalciferol 1000 IU daily. Bone mineral density and renal ultrasound were normal. Parathyroid ultrasound showed two hypoechoic nodules inferior to the left and right thyroid lobes; however, 99mtechnitium-sestamibi scans (2013, 2016, 2018) were negative. FCH-PET/CT (2019) showed focal uptake co-localizing with the nodule inferior to the left thyroid lobe. The patient underwent left inferior parathyroidectomy and pathology was consistent with parathyroid hyperplasia. However, postoperatively, serum calcium and PTH levels remained elevated and FCH-PET/CT and ultrasound showed persistence of the uptake/nodule. Whole exome sequencing showed Arg15Cys mutation in the AP2S1 gene characteristic of FHH type-3.

          Conclusions

          In this new case of FHH type-3, FCH-PET/CT failed to localize to the hyperplastic parathyroid glands and localized instead to apparently a lymph node. This, together with increased urinary calcium after vitamin D supplementation, led to unnecessary parathyroidectomy. Given the increasingly lower cost of genetic testing and the cost of follow up and unnecessary surgery, it may prudent to include genetic testing for FHH early on in patients with mild PTH-dependent hypercalcemia.

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          Most cited references40

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          Choline metabolism in malignant transformation.

          Abnormal choline metabolism is emerging as a metabolic hallmark that is associated with oncogenesis and tumour progression. Following transformation, the modulation of enzymes that control anabolic and catabolic pathways causes increased levels of choline-containing precursors and breakdown products of membrane phospholipids. These increased levels are associated with proliferation, and recent studies emphasize the complex reciprocal interactions between oncogenic signalling and choline metabolism. Because choline-containing compounds are detected by non-invasive magnetic resonance spectroscopy (MRS), increased levels of these compounds provide a non-invasive biomarker of transformation, staging and response to therapy. Furthermore, enzymes of choline metabolism, such as choline kinase, present novel targets for image-guided cancer therapy.
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            Hyperparathyroid and hypoparathyroid disorders.

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              Disorders of the calcium-sensing receptor and partner proteins: insights into the molecular basis of calcium homeostasis

              The extracellular calcium (Ca2+ o)-sensing receptor (CaSR) is a family C G protein-coupled receptor, which detects alterations in Ca2+ o concentrations and modulates parathyroid hormone secretion and urinary calcium excretion. The central role of the CaSR in Ca2+ o homeostasis has been highlighted by the identification of mutations affecting the CASR gene on chromosome 3q21.1. Loss-of-function CASR mutations cause familial hypocalciuric hypercalcaemia (FHH), whereas gain-of-function mutations lead to autosomal dominant hypocalcaemia (ADH). However, CASR mutations are only detected in ≤70% of FHH and ADH cases, referred to as FHH type 1 and ADH type 1, respectively, and studies in other FHH and ADH kindreds have revealed these disorders to be genetically heterogeneous. Thus, loss- and gain-of-function mutations of the GNA11 gene on chromosome 19p13.3, which encodes the G-protein α-11 (Gα11) subunit, lead to FHH type 2 and ADH type 2, respectively; whilst loss-of-function mutations of AP2S1 on chromosome 19q13.3, which encodes the adaptor-related protein complex 2 sigma (AP2σ) subunit, cause FHH type 3. These studies have demonstrated Gα11 to be a key mediator of downstream CaSR signal transduction, and also revealed a role for AP2σ, which is involved in clathrin-mediated endocytosis, in CaSR signalling and trafficking. Moreover, FHH type 3 has been demonstrated to represent a more severe FHH variant that may lead to symptomatic hypercalcaemia, low bone mineral density and cognitive dysfunction. In addition, calcimimetic and calcilytic drugs, which are positive and negative CaSR allosteric modulators, respectively, have been shown to be of potential benefit for these FHH and ADH disorders.
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                Author and article information

                Contributors
                nmukhtar42@kfshrc.edu.sa
                maboutaleb@kfshrc.edu.sa
                moqahtani@kfshrc.edu.sa
                muhammad@kfshrc.edu.sa
                Journal
                BMC Endocr Disord
                BMC Endocr Disord
                BMC Endocrine Disorders
                BioMed Central (London )
                1472-6823
                26 January 2021
                26 January 2021
                2021
                : 21
                : 20
                Affiliations
                [1 ]GRID grid.415310.2, ISNI 0000 0001 2191 4301, Department of Medicine , , King Faisal Specialist Hospital and Research Center, ; Riyadh, Saudi Arabia
                [2 ]GRID grid.415310.2, ISNI 0000 0001 2191 4301, Department of Radiology, , King Faisal Specialist Hospital, ; Riyadh, Saudi Arabia
                [3 ]GRID grid.411335.1, ISNI 0000 0004 1758 7207, Department of Cyclotron and Radiopharmaceuticals, , Alfaisal University, ; Riyadh, Saudi Arabia
                [4 ]GRID grid.415310.2, ISNI 0000 0001 2191 4301, Department of Clinical Studies and Empirical Ethics, , King Faisal Specialist Hospital and Research Centre, ; P O Box # 3354 (MBC 03), 11211 Riyadh, Saudi Arabia
                [5 ]GRID grid.411335.1, ISNI 0000 0004 1758 7207, College of Medicine, , Alfaisal University, ; Riyadh, Saudi Arabia
                Article
                683
                10.1186/s12902-021-00683-z
                7836468
                33499837
                d7ca52c2-10c4-4897-b32c-d75153d2c30a
                © The Author(s) 2021

                Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

                History
                : 26 November 2020
                : 19 January 2021
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/501100004919, King Abdulaziz City for Science and Technology;
                Award ID: 14-MED 1963-20
                Categories
                Case Report
                Custom metadata
                © The Author(s) 2021

                Endocrinology & Diabetes
                18f-fluorocholine positron emission tomography/ computed tomography,primary hyperparathyroidism,familial hypocalciuric hypercalcemia type-3,false positive localization

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