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Rob Gonsalves Division of Endocrinology, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Kirk Aleck Division of Genetics, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Dorothee Newbern Division of Endocrinology, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Gabriel Shaibi Division of Endocrinology, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Chirag Kapadia Division of Endocrinology, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Oliver Oatman Division of Endocrinology, Phoenix Children’s Hospital, Phoenix, Arizona, USA

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Summary

Single-minded homolog 1 (SIM1) is a transcription factor that plays a role in the development of both the hypothalamus and pituitary. SIM1 gene mutations are known to cause obesity in humans, and chromosomal deletions encompassing SIM1 and other genes necessary for pituitary development can cause a Prader–Willi-like syndrome with obesity and hypopituitarism. There have been no reported cases of hypopituitarism linked to a single SIM1 mutation. A 21-month-old male presented to endocrinology clinic with excessive weight gain and severe obesity. History was also notable for excessive drinking and urination. Endocrine workup revealed central hypothyroidism, partial diabetes insipidus, and central adrenal insufficiency. Genetic evaluation revealed a novel mutation in the SIM1 gene. No other genetic abnormalities to account for his obesity and hypopituitarism were identified. While we cannot definitively state this mutation is pathogenic, it is notable that SIM1 plays a role in the development of all three of the patient’s affected hormone axes. He is now 6 years old and remains on treatment for his pituitary hormone deficiencies and continues to exhibit excessive weight gain despite lifestyle interventions.

Learning points:

  • Mutations in SIM1 are a well-recognized cause of monogenic human obesity, and there have been case reports of Prader–Willi-like syndrome and hypopituitarism in patients with chromosomal deletions that contain the SIM1 gene.

  • SIM1 is expressed during the development of the hypothalamus, specifically in neuroendocrine lineages that give rise to the hormones oxytocin, arginine vasopressin, thyrotropin-releasing hormone, corticotropin-releasing hormone, and somatostatin.

  • Pituitary testing should be considered in patients with severe obesity and a known genetic abnormality affecting the SIM1 gene, particularly in the pediatric population.

Open access
Tu Vinh Luong The Department of Cellular Pathology, Royal Free London NHS Foundation Trust, London, UK
Neuroendocrine Tumour Unit, ENETS Center of Excellence, Royal Free London NHS Foundation Trust, London, UK

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Zaibun Nisa The Department of Cellular Pathology, Royal Free London NHS Foundation Trust, London, UK

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Jennifer Watkins The Department of Cellular Pathology, Royal Free London NHS Foundation Trust, London, UK
Neuroendocrine Tumour Unit, ENETS Center of Excellence, Royal Free London NHS Foundation Trust, London, UK

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Aimee R Hayes Neuroendocrine Tumour Unit, ENETS Center of Excellence, Royal Free London NHS Foundation Trust, London, UK
Department of Medical Oncology, Royal Free London NHS Foundation Trust, London, UK

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Summary

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) are typically associated with poor outcomes. The mechanisms of their aggressiveness are still being investigated. Microsatellite instability (MSI) has recently been found in colorectal NECs showing aberrant methylation of the MLH1 gene and is associated with improved prognosis. We present a 76-year-old lady with an ascending colon tumour showing features of a pT3 N0 R0, large cell NEC (LCNEC) following right hemicolectomy. The adjacent mucosa showed a sessile serrated lesion (SSL) with low-grade dysplasia. Immunohistochemistry showed loss of expression for MLH1 and PMS2 in both the LCNEC and dysplastic SSL. Molecular analysis indicated the sporadic nature of the MLH1 mismatch repair (MMR) protein-deficient status. Our patient did not receive adjuvant therapy and she is alive and disease-free after 34 months follow-up. This finding, similar to early-stage MMR-deficient colorectal adenocarcinoma, is likely practice-changing and will be critical in guiding the appropriate treatment pathway for these patients. We propose that testing of MMR status become routine for early-stage colorectal NECs.

Learning points:

  • Colorectal poorly differentiated neuroendocrine carcinomas (NECs) are known to be aggressive and typically associated with poor outcomes.

  • A subset of colorectal NECs can display microsatellite instability (MSI) with mismatch repair (MMR) protein-deficient status.

  • MMR-deficient colorectal NECs have been found to have a better prognosis compared with MMR-proficient NECs.

  • MMR status can be detected using immunohistochemistry.

  • Immunohistochemistry for MMR status is routinely performed for colorectal adenocarcinomas.

  • Immunohistochemical expression of MMR protein and MSI analysis should be performed routinely for early-stage colorectal NECs in order to identify a subgroup of MMR-deficient NECs which are associated with a significantly more favourable prognosis.

Open access
Jane J Tellam Royal Brisbane and Women’s Hospital, Herston, Queensland, Australia
University of Queensland, Herston, Queensland, Australia

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Ghusoon Abdulrasool Royal Brisbane and Women’s Hospital, Herston, Queensland, Australia
University of Queensland, Herston, Queensland, Australia
Pathology Queensland, Australia

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Louise C H Ciin Gold Coast University Hospital, Southport, Queensland, Australia
Griffith University, Southport, Queensland, Australia

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Summary

Distinguishing primary hyperparathyroidism (PHPT) from familial hypocalciuric hypercalcaemia (FHH) can be challenging. Currently, 24-h urinary calcium is used to differentiate between the two conditions in vitamin D replete patients, with urinary calcium creatinine clearance ratio (UCCR) <0.01 suggestive of FHH and >0.02 supportive of PHPT. A 26-year-old Caucasian gentleman presented with recurrent mild hypercalcaemia and inappropriately normal parathyroid hormone (PTH) following previous parathyroidectomy 3 years prior. He had symptoms of fatigue and light-headedness. He did not have any other symptoms of hypercalcaemia. His previous evaluation appeared to be consistent with PHPT as evidenced by hypercalcaemia with inappropriately normal PTH and UCCR of 0.0118 (borderline low using guidelines of >0.01 consistent with PHPT). He underwent parathyroidectomy and three parathyroid glands were removed. His calcium briefly normalised after surgery, but rose again to pre-surgery levels within 3 months. Subsequently, he presented to our centre and repeated investigations showed 24-h urinary calcium of 4.6 mmol/day and UCCR of 0.0081 which prompted assessment for FHH. His calcium-sensing receptor (CASR) gene was sequenced and a rare inactivating variant was detected. This variant was described once previously in the literature. His mother was also confirmed to have mild hypercalcaemia with hypocalciuria and, on further enquiry, had the same CASR variant. The CASR variant was classified as likely pathogenic and is consistent with the diagnosis of FHH. This case highlights the challenges in differentiating FHH from PHPT. Accurate diagnosis is vital to prevent unnecessary surgical intervention in the FHH population and is not always straightforward.

Learning points:

  • Distinguishing FHH from PHPT with co-existing vitamin D deficiency is difficult as this can mimic FHH. Therefore, ensure patients are vitamin D replete prior to performing 24-h urinary calcium collection.

  • Individuals with borderline UCCR could have either FHH or PHPT. Consider performing CASR gene sequencing for UCCR between 0.01 and 0.02.

  • Parathyroid imaging is not required for making the diagnosis of PHPT. It is performed when surgery is considered after confirming the diagnosis of PHPT.

Open access
J Pedro Department of Endocrinology, Diabetes and Metabolism, Centro Hospitalar Universitário de São João, Porto, Portugal
Faculty of Medicine of Universidade do Porto, Porto, Portugal

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F M Cunha Department of Endocrinology, Diabetes and Metabolism, Centro Hospitalar do Tâmega e Sousa, Penafiel, Portugal

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V Neto Department of Pneumology, Centro Hospitalar Universitário de São João, Porto, Portugal

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V Hespanhol Faculty of Medicine of Universidade do Porto, Porto, Portugal
Department of Pneumology, Centro Hospitalar Universitário de São João, Porto, Portugal
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal

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D F Martins Faculty of Medicine of Universidade do Porto, Porto, Portugal
Department of Pathology, Centro Hospitalar Universitário de São João, Porto, Portugal

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S Guimarães Department of Pathology, Centro Hospitalar Universitário de São João, Porto, Portugal

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A Varela Department of Endocrinology, Diabetes and Metabolism, Centro Hospitalar Universitário de São João, Porto, Portugal
Faculty of Medicine of Universidade do Porto, Porto, Portugal
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal

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D Carvalho Department of Endocrinology, Diabetes and Metabolism, Centro Hospitalar Universitário de São João, Porto, Portugal
Faculty of Medicine of Universidade do Porto, Porto, Portugal
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal

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Summary

We describe the case of a 56 year-old woman with the almost simultaneous appearance of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) and a carotid body paraganglioma. Of interest, 6 years earlier, the patient underwent total thyroidectomy due to papillary thyroid carcinoma and, in the meantime, she was submitted to mastectomy to treat an invasive ductal carcinoma of the breast. In order to explain these lesions, an extensive genetic study was performed. Results showed positivity for the presence of the tumor suppressor gene PALB2, whose presence had already been detected in a niece with breast cancer. The patient underwent different procedures to treat the lesions and currently she is symptom-free over 2 years of follow-up.

Learning points:

  • The presence of two rare neoplasms in a single person should raise the suspicion of a common etiology.

  • To the best of our knowledge, this is the first case that shows the coexistence of DIPNECH and paraganglioma.

  • The contribution of the PALB2 gene in the etiology of these rare neoplasms is a possibility.