Diagnosis and stabilisation of familial chylomicronemia syndrome in two infants presenting with hypertriglyceridemia-induced acute pancreatitis.

Familial chylomicronemia syndrome (FCS) is a rare disorder of triglyceride (TG) metabolism caused by loss of function variants in one of five known canonical genes involved in chylomicron lipolysis and clearance-LPL, APOC2, APOA5, LMF1, and GPIHBP1. Pathogenic variants in LPL, which encodes the hydrolytic enzyme lipoprotein lipase, account for over 80%-90% of cases. FCS may present in infancy with hypertriglyceridemia-induced acute pancreatitis and is challenging to manage both acutely and in the long-term. Here, we report our experience managing two unrelated infants consecutively diagnosed with hypertriglyceridemia-induced acute pancreatitis caused by LPL deficiency. Both had elevated TGs at presentation (205 and 30 mmol/L, respectively) and molecular genetic testing confirmed each infant carried a different homozygous pathogenic variant in the LPL gene, specifically, c.987C>A (p.Tyr329Ter) and c.632C>A (p.Thr211Lys). The more severely affected infant had cutaneous xanthomata, lipemia retinalis and lipemic plasma at presentation, and required management in an intensive care setting. Acute stabilisation was achieved using insulin and heparin infusions together with the iterative implementation of a fat-restricted diet, low in long chain triglycerides (LCT) and supplemented with medium chain triglycerides (MCT). In both cases, provision of adequate caloric intake (~110-120 kcal/kg/day) was also found to be important for a sustained TG reduction during the acute phase of management. In summary, a high index of suspicion is required to diagnose FCS in infants with hypertriglyceridemia-induced acute pancreatitis, management of which can be challenging, highlighting the need for more evidence-based recommendations.

Ending an Odyssey? The Psychosocial Experiences of Parents after the Genetic Diagnosis of a Mitochondrial Disease in Children.

Obtaining a genetic diagnosis of a primary mitochondrial disease (PMD) is often framed as a diagnostic odyssey. Yet, even after receiving a diagnosis, parents of affected children experience ongoing therapeutic and prognostic uncertainty and considerable psychosocial challenges. Semi-structured interviews (N = 24) were conducted with parents of 13 children (aged 2-19 years) with a genetically confirmed PMD. Paternal (N = 11) and maternal (N = 13) perspectives were obtained, and thematic analysis was performed on all interviews. A genetic diagnosis was valuable and empowering for parents, despite eliciting varied emotional responses. While the diagnosis helped focus management decisions, families often felt overwhelmed and unsupported in navigating the healthcare system. Most parents reported a serious impact on their romantic relationship. The sources of social support varied, with a preference for established friendship and family support networks over disease-specific community support groups. Most parents favored prenatal genetic testing in the event of a future pregnancy. This study provides insight into the lived experiences of parents after a genetic diagnosis of PMD in their children. The findings draw awareness to supportive care needs and highlight important gaps that should be addressed to ensure that parents feel supported within a holistic framework of management for PMDs.

A metabolic signature for NADSYN1-dependent congenital NAD deficiency disorder.

Nicotinamide adenine dinucleotide (NAD) is essential for embryonic development. To date, biallelic loss-of-function variants in 3 genes encoding nonredundant enzymes of the NAD de novo synthesis pathway - KYNU, HAAO, and NADSYN1 - have been identified in humans with congenital malformations defined as congenital NAD deficiency disorder (CNDD). Here, we identified 13 further individuals with biallelic NADSYN1 variants predicted to be damaging, and phenotypes ranging from multiple severe malformations to the complete absence of malformation. Enzymatic assessment of variant deleteriousness in vitro revealed protein domain-specific perturbation, complemented by protein structure modeling in silico. We reproduced NADSYN1-dependent CNDD in mice and assessed various maternal NAD precursor supplementation strategies to prevent adverse pregnancy outcomes. While for Nadsyn1+/- mothers, any B3 vitamer was suitable to raise NAD, preventing embryo loss and malformation, Nadsyn1-/- mothers required supplementation with amidated NAD precursors (nicotinamide or nicotinamide mononucleotide) bypassing their metabolic block. The circulatory NAD metabolome in mice and humans before and after NAD precursor supplementation revealed a consistent metabolic signature with utility for patient identification. Our data collectively improve clinical diagnostics of NADSYN1-dependent CNDD, provide guidance for the therapeutic prevention of CNDD, and suggest an ongoing need to maintain NAD levels via amidated NAD precursor supplementation after birth.