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Early infantile Krabbe disease is rapidly fatal, but hematopoietic stem cell transplantation (HSCT) may improve outcomes if performed soon after birth. New York State began screening all newborns for Krabbe disease in 2006. Infants with abnormal newborn screen results for Krabbe disease were referred to specialty-care centers. Newborns found to be at high risk for Krabbe disease underwent a neurodiagnostic battery to determine the need for emergent HSCT. Almost 2 million infants were screened. Five infants were diagnosed with early infantile Krabbe disease. Three died, two from HSCT-related complications and one from untreated disease. Two children who received HSCT have moderate to severe developmental delays. Forty-six currently asymptomatic children are considered to be at moderate or high risk for development of later-onset Krabbe disease. These results show significant HSCT-associated morbidity and mortality in early infantile Krabbe disease and raise questions about its efficacy when performed in newborns diagnosed through newborn screening. The unanticipated identification of “at risk” children introduces unique ethical and medicolegal issues. New York’s experience raises questions about the risks, benefits, and practicality of screening newborns for Krabbe disease. It is imperative that objective assessments be made on an ongoing basis as additional states begin screening for this disorder. Genet Med18 12, 1235–1243.

Krabbe disease (KD) results from galactocerebrosidase (GALC) deficiency. Infantile KD symptoms include irritability, progressive stiffness, developmental delay, and death. The only potential treatment is hematopoietic stem cell transplantation. New York State (NYS) implemented newborn screening for KD in 2006. Dried blood spots from newborns were assayed for GALC enzyme activity using mass spectrometry, followed by molecular analysis for those with low activity (≤12% of the daily mean). Infants with low enzyme activity and one or more mutations were referred for follow-up diagnostic testing and neurological examination. Of >1.9 million screened, 620 infants were subjected to molecular analysis and 348 were referred for diagnostic testing. Five had enzyme activities and mutations consistent with infantile KD and manifested clinical/neurodiagnostic abnormalities. Four underwent transplantation, two are surviving with moderate to severe handicaps, and two died from transplant-related complications. The significance of many sequence variants identified is unknown. Forty-six asymptomatic infants were found to be at moderate to high risk for disease. The positive predictive value of KD screening in NYS is 1.4% (5/346) considering confirmed infantile cases. The incidence of infantile KD in NYS is approximately 1 in 394,000, but it may be higher for later-onset forms.

Purpose Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations. Methods PSY was extracted from dried blood spots or erythrocytes with methanol containing d 5 -PSY as internal standard, and measured by liquid chromatography–tandem mass spectrometry. Results Analysis of PSY in samples from controls ( N  = 209), GALC pseudodeficiency carriers ( N  = 55), GALC pathogenic variant carriers ( N  = 27), patients with infantile KD ( N  = 26), and patients with late-onset KD ( N  = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT). Conclusion This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.

Purpose The implementation of newborn screening for lysosomal disorders has uncovered overall poor specificity, psychosocial harm experienced by caregivers, and costly follow-up testing of false-positive cases. We report an informatics solution proven to minimize these issues. Methods The Kentucky Department for Public Health outsourced testing for mucopolysaccharidosis type I (MPS I) and Pompe disease, conditions recently added to the recommended uniform screening panel, plus Krabbe disease, which was added by legislative mandate. A total of 55,161 specimens were collected from infants born over 1 year starting from February 2016. Testing by tandem mass spectrometry was integrated with multivariate pattern recognition software (Collaborative Laboratory Integrated Reports), which is freely available to newborn screening programs for selection of cases for which a biochemical second-tier test is needed. Results Of five presumptive positive cases, one was affected with infantile Krabbe disease, two with Pompe disease, and one with MPS I. The remaining case was a heterozygote for the latter condition. The false-positive rate was 0.0018% and the positive predictive value was 80%. Conclusion Postanalytical interpretive tools can drastically reduce false-positive outcomes, with preliminary evidence of no greater risk of false-negative events, still to be verified by long-term surveillance.

Lysosomal storage diseases (LSDs) are typically caused by a deficiency in a soluble acid hydrolase and are characterized by the accumulation of undegraded substrates in the lysosome. Determining the role of specific cell types in the pathogenesis of LSDs is a major challenge due to the secretion and subsequent uptake of lysosomal hydrolases by adjacent cells, often referred to as “cross-correction.” Here we create and validate a conditional mouse model for cell-autonomous expression of galactocerebrosidase (GALC), the lysosomal enzyme deficient in Krabbe disease. We show that lysosomal membrane-tethered GALC (GALCLAMP1) retains enzyme activity, is able to cleave galactosylsphingosine, and is unable to cross-correct. Ubiquitous expression of GALCLAMP1 fully rescues the phenotype of the GALC-deficient mouse (Twitcher), and widespread deletion of GALCLAMP1 recapitulates the Twitcher phenotype. We demonstrate the utility of this model by deleting GALCLAMP1 specifically in myelinating Schwann cells in order to characterize the peripheral neuropathy seen in Krabbe disease.

Aim This study aims to expand the clinical and genetic spectrum of Krabbe disease (KD) in Chinese adult patients and to improve diagnosis and understanding of its phenotypic diversity. Methods Patients clinically suspected of leukodystrophy were recruited between 2015 and 2025. Clinical features were collected, and whole‐exome sequencing (WES) was performed to identify potential variants. The pathogenicity of detected variants was classified according to the American College of Medical Genetics and Genomics (ACMG) standards and guidelines. Functional assays assessing protein expression, processing, secretion, subcellular localization, and enzymatic activity were conducted to further validate variant pathogenicity. Results Fourteen unrelated patients were genetically diagnosed with KD, and their genetic and clinical features were summarized. Eleven variants in GALC were identified, including a novel missense variant c.1019C>T (p.P340L) which is not reported in the Human Gene Mutation Database (HGMD). Unlike most adult patients who typically present with spastic paraplegia, the patient carrying this variant exhibited initial symptoms of peripheral neuropathy. Functional experiments demonstrated that the variant led to impaired protein processing and localization, as well as reduced GALC enzymatic activity. Other variants including p.D56H, p.L377X, p.L441X, and p.L634S also affected GALC functions to varying degrees. Conclusion This study enhances the genotypic and phenotypic characterization of KD in China, aiding in differential diagnosis and genetic counseling. Functional data reinforce the pathogenicity of identified variants. This study presents a comprehensive analysis of the genetic and clinical spectrum of Krabbe disease in a Chinese cohort, with a particular focus on adult‐onset cases. We identified 11 GALC variants, including the novel mutation p.P340L, and provided functional evidence supporting its pathogenicity through impaired protein processing, mislocalization, and reduced enzymatic activity. The clinical heterogeneity observed highlights the diagnostic challenge of adult‐onset Krabbe disease.

Leukodystrophies are white matter disorders that are genetic in nature. In the young, they represent an important cause of progressive neurological disability. They are frequently recognized on MRI, but their identification remains a challenge. Their diagnosis is important for prognostication, palliative and experimental treatment, as well as family screening. The diagnostic strategy rests upon clinical clues and MRI patterns, complemented by appropriately selected electrophysiological and laboratory testing. Considerable overlap exists between white and gray matter disease, as neuronal degeneration will result in myelin loss. An understanding of the pathophysiology and natural disease evolution is necessary to understand the risks and benefits of experimental and palliative treatments.

Objective Krabbe disease is due to deficiency of galactocerebrosidase, resulting in progressive neurodegeneration due to demyelination. The purpose of this study is to document disease progression in the newly classified infantile‐onset (0–12 months). We evaluated the outcomes of hematopoietic stem cell transplantation (HSCT) and described meaningful clinical endpoints. Methods Patients with infantile Krabbe disease were prospectively evaluated between 2000 and 2022. All patients underwent comprehensive and standardized protocols. Descriptive statistics and Kaplan–Meier survival curves were used for analysis. Results One hundred and thirty‐seven children with infantile Krabbe disease were included (68 males and 69 females). Of the 137, 96 were not treated and 41 underwent hematopoietic stem cell transplantation. Twenty‐three were asymptomatic and 18 symptomatic. Initial symptoms included irritability, developmental delay or loss of milestones, feeding difficulties, spasticity, and reflux with an average survival of 2.2. Abnormalities in nerve conduction studies, auditory brainstem responses, and brain MRIs were evident in both groups of patients. Age at transplantation and signs and symptoms determined functional outcomes. Symptomatic and asymptomatic transplanted patients showed an increase in galactocerebrosidase and a decrease in psychosine, but did not reach the normal range. The median survival for transplanted symptomatic patients was 5 years while asymptomatic was extended to 15.5 years. Interpretation Infantile Krabbe disease with onset before 12 months is rapidly progressive. Irreversible brain damage occurs unless timely HSCT is performed. HSCT does not prevent the progression of peripheral nerve disease. This study can be used to monitor patients and evaluate the effects of future therapies.

Krabbe disease usually presents as a severe leukodystrophy in early infancy and childhood. From a series of 11 patients and 30 cases previously reported in the literature we describe the clinical, radiological, electrophysiological and genetic features of adult Krabbe disease. Patients diagnosed after the age of 16 years were included in this study. They were further divided into three groups depending on age at symptoms onset: (1) childhood onset cases ( n  = 7); (2) adolescence onset cases ( n  = 6) and adult onset cases ( n  = 28). Overall, 96 % of patients in the adult-onset group presented with signs of pyramidal tracts dysfunction. Spastic paraparesis or tetraparesis became prominent in all cases. A peripheral neuropathy was present in 59 % of cases and was most often demyelinating (80 %). Other clinical signs encompassed dysarthria (31 %), cerebellar ataxia (27 %), pes cavus (27 %), deep sensory signs (23 %), tongue atrophy (15 %), optic neuropathy (12 %), cognitive decline (12 %). Cerebrospinal fluid protein concentration was moderately increased in 54 % of patients. Patients in the adolescent- and childhood-onset groups had similar presentations but were more likely to display optic neuropathy (33 % and 57 %) and cerebellar ataxia (50 % and 57 %). In the adult-onset group, the disease progressed slowly over more than 10 years, but a rapid course was observed in two patients. Abnormalities of brain MRI was similar in the three groups and included high signals of cortico-spinal tracts (94 % of cases), hyper-intensities of optic radiations (89 %) and hyper-intensities or atrophy of the posterior part of the corpus callosum (60 %). No clear genotype-phenotype relationship could be demonstrated.