A missense variant in SLC12A3 gene enhances aberrant splicing causing Gitelman syndrome.

Gitelman syndrome (GS) is the most prevalent genetic tubulopathy characterized by several electrolyte abnormalities, including hypokalemia, hypomagnesemia, hypocalciuria, metabolic alkalosis, and hyperreninemic hyperaldosteronism. These features are caused by a bi-allelic mutation in the SLC12A3 gene. In this report, we present a case of GS in an asymptomatic woman who incidentally exhibited hypokalemia during an antenatal check-up. Her biochemical profile was consistent with GS. Genetic analysis revealed two heterozygous variants in trans, namely, NM_001126108.2:c.625C>T; p.(Arg209Trp) and c.965C>T; p.(Ala322Val). The c.625C>T; p.(Arg209Trp) variant has previously been experimentally confirmed as a loss-of-function (LOF) variant. However, the functional impact of the c.965C>T variant, located at the 5 prime end of exon 8, has not been fully elucidated. Through the utilization of both complementary DNA (cDNA) and minigene analysis, we confirmed that the c.965C>T variant can generate two distinct cDNA transcripts. The first transcript carries a missense mutation, p.(Ala322Val) in the full SLC12A3 transcript, while the second transcript consists of an in-frame deletion of both exons 7 and 8 in the SLC12A3 transcript, in which may result in the loss of transmembrane regions 5 - 6 involved in chloride transport. Our findings provide insights into the intricate mechanisms of splicing, highlighting how a variant in one exon can remotely influence the transcription of an upstream exon, as observed with the variant in exon 8 impacting the transcription of exon 7.

A clinicopathological study of non-functioning pituitary neuroendocrine tumours using the World Health Organization 2022 classification.

Background: The 2022 World Health Organization (WHO) classification of pituitary neuroendocrine tumour (PitNET) supersedes the previous one in 2017 and further consolidates the role of transcription factors (TF) in the diagnosis of PitNET. Here, we investigated the clinical utility of the 2022 WHO classification, as compared to that of 2017, in a cohort of patients with non-functioning PitNET (NF-PitNET). Methods: A total of 113 NF-PitNET patients who underwent resection between 2010 and 2021, and had follow-up at Queen Mary Hospital, Hong Kong, were recruited. Surgical specimens were re-stained for the three TF: steroidogenic factor (SF-1), T-box family member TBX19 (TPIT) and POU class 1 homeobox 1 (Pit-1). The associations of different NF-PitNET subtypes with tumour-related outcomes were evaluated by logistic and Cox regression analyses. Results: Based on the 2022 WHO classification, the majority of NF-PitNET was SF-1-lineage tumours (58.4%), followed by TPIT-lineage tumours (18.6%), tumours with no distinct lineage (16.8%) and Pit-1-lineage tumours (6.2%). Despite fewer entities than the 2017 classification, significant differences in disease-free survival were present amongst these four subtypes (Log-rank test p=0.003), specifically between SF-1-lineage PitNET and PitNET without distinct lineage (Log-rank test p<0.001). In multivariable Cox regression analysis, the subtype of PitNET without distinct lineage (HR 3.02, 95% CI 1.28-7.16, p=0.012), together with tumour volume (HR 1.04, 95% CI 1.01-1.07, p=0.017), were independent predictors of a composite of residual or recurrent disease. Conclusion: The 2022 WHO classification of PitNET is a clinically useful TF and lineage-based system for subtyping NF-PitNET with different tumour behaviour and prognosis.

Cushing's syndrome caused by ACTH precursors secreted from a pancreatic yolk sac tumor in an adult-a case report and literature review.

Here, we report the first adult case of pancreatic yolk sac tumor with ectopic adrenocorticotropic hormone (ACTH) syndrome. The patient was a 27-year-old woman presenting with abdominal distension, Cushingoid features, and hyperpigmentation. Endogenous Cushing's syndrome was biochemically confirmed. The ACTH level was in the normal range, which raised the suspicion of ACTH precursor-dependent disease. Elevated ACTH precursors were detected, supporting the diagnosis of ectopic ACTH syndrome. Functional imaging followed by tissue sampling revealed a pancreatic yolk sac tumor. The final diagnosis was Cushing's syndrome due to a yolk sac tumor. The patient received a steroidogenesis inhibitor and subsequent bilateral adrenalectomy for control of hypercortisolism. Her yolk sac tumor was treated with chemotherapy and targeted therapy. Cushing's syndrome secondary to a yolk sac tumor is extremely rare. This case illustrated the utility of ACTH precursor measurement in confirming an ACTH-related pathology and distinguishing an ectopic from a pituitary source for Cushing's syndrome.

Case Report: Insulinoma Co-Existing With Type 2 Diabetes - Advantages and Challenges of Treatment With Endoscopic Ultrasound-Guided Radiofrequency Ablation.

The coexistence of insulinoma and type 2 diabetes is rare and the diagnostic process is often challenging. Continuous glucose monitoring system devices, which are more readily available nowadays, provide a useful tool for the diagnosis and evaluation of treatment response. Curative surgery is often the mainstay of treatment for insulinoma. Here, we report a Chinese patient with insulinoma diagnosed simultaneously with type 2 diabetes. His insulinoma was managed with endoscopic ultrasound guided-radiofrequency ablation (EUS-RFA) and the patient achieved complete resolution of hypoglycaemic episodes. The case illustrates that while EUS-RFA is an emerging non-invasive treatment modality for pancreatic lesions, limitations exist especially when histological confirmation is essential.