Matern, Dietrich

Krabbe disease is an autosomal recessive leukodystrophy caused by a deficiency of the lysosomal enzyme galactosylceramidase (GALC), responsible for the degradation of galactolipids, resulting in toxic psychosine accumulation and progressive demyelination of the central and peripheral nervous systems. Newborn screening (NBS) has increased recognition of later-onset Krabbe disease, although interpretation of complex GALC genotypes remains challenging, particularly in the presence of “pseudodeficiency” and modifier alleles. In this case report, we describe a child with late-infantile Krabbe disease identified through NBS with markedly reduced GALC activity and a homozygous GALC haplotype containing c.956A>G (p.Tyr319Cys; Y319C) and c.1685T>C (p.Ile562Thr; I562T), in addition to other benign variants. Retrospective analysis of the newborn screening specimen demonstrated mild psychosine elevation. Despite preserved neurodevelopment, longitudinal surveillance demonstrated progressive cerebral white matter abnormalities by 3 years and 9 months of age and psychosine elevation in erythrocytes (14 pmol/g Hb; controls < 5), prompting umbilical cord blood transplantation (UCBT). Following transplantation, GALC enzyme activity normalized, psychosine levels decreased, and serial neuroimaging demonstrated radiographic stability without neurologic regression at last follow-up (9 years old). This case expands the phenotypic spectrum associated with homozygosity for the p.Tyr319Cys variant and highlights the role of p.Ile562Thr in amplifying the pathogenic potential when in cis with p.Tyr319Cys. This GALC haplotype illustrates how “pseudodeficiency” and modifier alleles may collectively influence biochemical, radiologic, and clinical disease expression. These findings emphasize the importance of integrating genotype, psychosine, enzyme activity, and longitudinal neuroimaging when evaluating infants with NBS results positive for Krabbe disease.

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 3‐hydroxy acylcarnitines (3‐OH‐ACs) are key biomarkers for screening of long‐chain 3‐hydroxyacyl‐CoA dehydrogenase and trifunctional protein deficiencies (LCHADD/TFPD). The utility of this biomarker for disease monitoring in identified patients remains debated, and recent suggestions have highlighted the potential use of lipidomics for diagnosis, monitoring, prognosis, and/or identification of new biomarkers. We evaluated the use of omics in LCHADD/TFPD patients by analyzing plasma acylcarnitine profiles, metabolomics, and lipidomics, combined with genotype, visual assessments, and dietary records. Fasting plasma from 39 participants with LCHADD/TFPD and 32 control subjects were analyzed through untargeted metabolomic and lipidomic analyses. In LCHADD/TFPD participants, acylcarnitine profiling, visual and retinal function assessments were performed, and 3‐day diet records were collected. Relationships between acylcarnitines, metabolomics, lipidomics, along with visual outcomes and dietary intake were investigated. Plasma of LCHADD/TFPD participants exhibited elevated 3‐OH‐ACs, which correlated with genotype and visual outcomes. Metabolomics successfully distinguished LCHADD/TFPD from controls, and the biggest divergence was observed in lipid pathways. Metabolomic profiles tightly correlated with 3‐OH‐ACs, genotype, and visual outcomes. Lower concentrations of total lipids and some individual lipid species such as phosphoethanolamines (PE) were detected in LCHADD/TFPD, except for elevations in several certain triglycerides. LCHADD/TFPD participants followed a diet low in long‐chain fat (LCFA) as recommended. LCFA intake did not correlate with either plasma 3‐OH‐ACs or metabolomics. 3‐OH‐ACs are strong consistent biomarkers of LCHADD/TFPD that are associated with clinical parameters of vision and genotype. We did not observe a relationship between dietary LCFA intake and 3‐OH‐ACs.

Abstract Background Sphingolipids play a crucial role in cellular functions and are essential components of cell membranes, signaling molecules, and lipid metabolism. In particular, ceramide is a key intermediate in sphingolipid metabolism and defects in ceramide metabolism can lead to various inborn errors of metabolism, making ceramides important targets for clinical screening and diagnosis. Detecting altered concentration patterns of sphingolipids is desirable for distinguishing related inborn errors of metabolism for diagnosis and treatment monitoring. Methods We developed a liquid chromatography-tandem mass spectrometry method with a pathway-oriented approach to focus on sphingolipids involved in ceramide metabolism. A total of 47 sphingolipids bearing different head groups and side chains were targeted. Precision/reproducibility, linearity, and spike recovery extraction efficiency tests were performed on plasma and serum samples from confirmed cases of sphingolipidosis. Results Linearity of the method showed the coefficient of determination (r2) for all standards to be &gt;0.99 with a slope of 1.00 ± 0.01. Intra- and interday reproducibility of standards spiked into plasma and serum revealed a coefficient of variation &lt;20%. Spike and recovery assessment showed recovery values of 80%–120% for all standards. Altered levels of sphingolipids from patients with hereditary sensory and autonomic neuropathy caused by pathogenic variants in SPTLC2 and hypomyelinating leukodystrophy related to variants in DEGS1 were detected, in agreement with trends reported in earlier studies confirming the utility of this pathway-centric method. Conclusions This method can serve as a useful tool to simultaneously monitor sphingolipids, enabling screening and diagnosis of inborn errors of ceramide metabolism.