Background Idiopathic Ketotic hypoglycemia (IKH) is a diagnosis of exclusion. Although considered as the most frequent cause of hypoglycemia in childhood, little progress has been made to advance the understanding of IKH since the medical term was coined in 1964. We aimed to review the literature on ketotic hypoglycemia (KH) and introduce a novel patient organization, Ketotic Hypoglycemia International (KHI). Results IKH may be diagnosed after the exclusion of various metabolic and hormonal diseases with KH. Although often mild and self-limiting, more severe and long-lasting IKH occurs. We therefore divide IKH in physiological KH and pathological KH, the latter defined as recurrent symptomatic, or occasionally symptomatic, episodes with beta-hydroxybutyrate ≥ 1.0 mmol/L and blood glucose < 70 mg/dL (3.9 mol/L), in the absence of prolonged fasting, acute infections and chronic diseases known to cause KH. Pathological KH may represent undiscovered diseases, e.g. glycogen storage disease IXa, Silver–Russel syndrome, and ketone transporter defects, or suggested novel disease entities identified by exome sequencing. The management of KH aims to prevent hypoglycemia, fatty acid oxidation and protein deficiency by supplying adequate amounts of carbohydrates and protein, including nutritional therapy, uncooked cornstarch, and sometimes continuous tube feeding by night. Still, intravenous dextrose may be needed in acute KH episodes. Failure to acknowledge that IKH can be more than normal variation may lead to under-treatment. KHI is a non-profit, patient-centric, global organization established in 2020. The organization was created by adult IKH patients, patient family members, and volunteers. The mission of KHI is to enhance the understanding of IKH while advocating for patients, their families and the continued research into KH. Conclusion IKH is a heterogeneous disorder including physiological KH and pathological KH. IKH may represent missed diagnoses or novel disease entities, but shares common management principles to prevent fatty acid oxygenation. KHI, a novel patient organization, aims to enhance the understanding of IKH by supporting IKH families and research into IKH.

Background: Ketotic hypoglycemia (KH) without an identifiable underlying metabolic or hormonal disease is historically named idiopathic KH. The prevalence is unknown, but idiopathic KH is considered the most frequent cause of hypoglycemia beyond the neonatal period. KH in Down syndrome (DS) has not been reported. Methods:We conducted a web-based survey on KH in DS through the nonprofit patient organization Ketotic Hypoglycemia International. The responses were evaluated for consistency with KH by two authors. Two DS patient histories with documented KH were shared in more details. Results: Survey data on 139 DS patients were obtained. After validation, 10 patients (7.2%) had reported episodes of documented hypoglycemia, ketosis, and/or symptoms compatible with KH beyond the neonatal period. Glucose concentrations ranged 1.2-2.9 mmol/L; betahydroxybutyrate was up to 5.5 mmol/L during hypoglycemia. One girl had trisomy 21 with no response to i.m. glucagon also had a heterozygous Xp22.23 deletion including GYG2, which protein, glycogenin 2, is a substrate for glycogen synthase. Treatment with extended release cornstarch was effective.Conclusion: This is the first demonstration of a possible high prevalence of KH in DS. Even though this finding needs to be confirmed in other research settings, identification of KH in DS could have a dramatic impact, as simple treatments with cornstarch, protein and frequent meals may prevent KH attacks and, analogous to other conditions with KH, improve growth, stamina and prevent overeating and obesity. GYG2 deletion may contribute to KH in DS, resembling glycogen storage disease type 0.

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