Coman, David

COASY-related disorders (CRDs) are a spectrum of autosomal recessive conditions caused by the dysfunction of CoA synthase, an enzyme responsible for the final steps of CoA synthesis. Clinical manifestations of CRDs are highly variable, ranging from perinatal lethal pontocerebellar hypoplasia to childhood-onset neurodegenerative brain iron accumulation, which is often recognized after clinical regression. Recent reports have described a few individuals with CRD who screened positive for carnitine palmitoyltransferase-I deficiency by newborn screening (NBS). However, heterogeneous clinical presentations, conflicting biochemical/molecular sequencing of CPT1A, and a lack of metabolic characterization have led to lengthy, costly diagnostic journeys. To address some of these aspects, this investigation retrospectively evaluated NBS acylcarnitine patterns in five CRD cases using Collaborative Laboratory Integrated Reports (CLIR). A total of 25 metabolites/ratios were identified to deviate significantly from reference ranges and were primarily composed of elevated free carnitine and reduced long-chain acylcarnitine levels. While low acylcarnitine concentrations are often not reported due to a lack of lower reference cutoffs, ratios involving these metabolites relative to short-chain acylcarnitines could aid in identifying CRD cases via NBS. When comparing this pattern to CPT-Ia cases, we confirmed a nearly identical acylcarnitine pattern between these, and thus support the need to consider CRD in cases with NBS results suggestive of CPT-Ia. This study is the first case series to characterize NBS patterns in patients with CRD and highlights the unique opportunity for early detection, particularly in cases that are neonatally asymptomatic and have unremarkable confirmatory biochemical results.

Abstract Phosphoglucomutase 1 (PGM1) deficiency is a rare genetic disorder that affects glycogen metabolism, glycolysis, and protein glycosylation. Previously known as GSD XIV, it was recently reclassified as a congenital disorder of glycosylation, PGM1‐CDG. PGM1‐CDG usually manifests as a multisystem disease. Most patients present as infants with cleft palate, liver function abnormalities and hypoglycemia, but some patients present in adulthood with isolated muscle involvement. Some patients develop life‐threatening cardiomyopathy. Unlike most other CDG, PGM1‐CDG has an effective treatment option, d ‐galactose, which has been shown to improve many of the patients' symptoms. Therefore, early diagnosis and initiation of treatment for PGM1‐CDG patients are crucial decisions. In this article, our group of international experts suggests diagnostic, follow‐up, and management guidelines for PGM1‐CDG. These guidelines are based on the best available evidence‐based data and experts' opinions aiming to provide a practical resource for health care providers to facilitate successful diagnosis and optimal management of PGM1‐CDG patients.

Abstract Background Phosphomannomutase 2 deficiency (PMM2‐CDG) is the most common congenital disorder of glycosylation (CDG). Hypoglycemia has been reported in various CDG including PMM2‐CDG. The frequency and etiology of hypoglycemia in PMM2‐CDG are not well studied. Methods We conducted a systematic review of the literature on genetically and/or biochemically confirmed PMM2‐CDG patients who developed hypoglycemia. Prospective follow‐up information on the patients who received diazoxide therapy was collected and evaluated. Results A total of 165 peer‐reviewed articles reporting on 933 PMM2‐CDG patients were assessed. Hypoglycemia was specifically mentioned only in 23 of these patients (2.5%). Hyperinsulinism was identified in 10 patients (43% of all hypoglycemic patients). Among these 10 patients, seven were successfully treated with diazoxide. However, most patients remained on therapy longer than a year to stay free of hypoglycemia. Conclusion Hypoglycemia is a rarely reported finding in patients with PMM2‐CDG. Diazoxide‐responsive hyperinsulinism was found to have a good prognosis on medication in our PMM2‐CDG patients with hypoglycemia. No genotype‐phenotype correlation was observed with respect to hyperinsulinism. A prospective study should be undertaken to explore the hypothesis that hypoglycemia is underdiagnosed in PMM2‐CDG and to evaluate whether hyperinsulinism is always associated with hypoglycemia.

Abstract Phosphomannomutase 2 (PMM2‐CDG) is the most common congenital disorder of N‐glycosylation and is caused by a deficient PMM2 activity. The clinical presentation and the onset of PMM2‐CDG vary among affected individuals ranging from a severe antenatal presentation with multisystem involvement to mild adulthood presentation limited to minor neurological involvement. Management of affected patients requires a multidisciplinary approach. In this article, a systematic review of the literature on PMM2‐CDG was conducted by a group of international experts in different aspects of CDG. Our managment guidelines were initiated based on the available evidence‐based data and experts' opinions. This guideline mainly addresses the clinical evaluation of each system/organ involved in PMM2‐CDG, and the recommended management approach. It is the first systematic review of current practices in PMM2‐CDG and the first guidelines aiming at establishing a practical approach to the recognition, diagnosis and management of PMM2‐CDG patients.