Newborn screening for acid sphingomyelinase deficiency in Illinois: A single center's experience.

Acid sphingomyelinase deficiency (ASMD) is a rare lysosomal storage disorder (LSD) caused by reduced activity of the acid sphingomyelinase (ASM) enzyme, which leads to progressive storage of sphingomyelin and related lipids in the body. ASMD is caused by biallelic variants in the SMPD1 gene, which encodes for the ASM enzyme. Current estimates of disease incidence range from 0.4 to 0.6 in 100 000 livebirths, although this is likely an underestimation of the true frequency of the disorder. While there is no cure for ASMD, comprehensive care guidelines and enzyme replacement therapy are available, making an early diagnosis crucial. Newborn screening (NBS) for ASMD is possible through measurement of ASM activity in dried blood spots and offers the opportunity for early diagnosis. In 2015, Illinois (IL) became the first to initiate statewide implementation of NBS for ASMD. This study describes the outcomes of screen-positive patients referred to Ann & Robert H. Lurie Children's Hospital (Lurie). Ten infants were referred for diagnostic evaluation at Lurie, and all 10 infants were classified as confirmed ASMD or at risk for ASMD through a combination of molecular and biochemical testing. Disease incidence was calculated using data from this statewide implementation program and was ~0.79 in 100 000 livebirths. This study demonstrates successful implementation of NBS for ASMD in IL, with high screen specificity and a notable absence of false positive screens.

De novo missense variants in exon 9 of SEPHS1 cause a neurodevelopmental condition with developmental delay, poor growth, hypotonia, and dysmorphic features.

Selenophosphate synthetase (SEPHS) plays an essential role in selenium metabolism. Two mammalian SEPHS paralogues, SEPHS1 and SEPHS2, share high sequence identity and structural homology with SEPHS. Here, we report nine individuals from eight families with developmental delay, growth and feeding problems, hypotonia, and dysmorphic features, all with heterozygous missense variants in SEPHS1. Eight of these individuals had a recurrent variant at amino acid position 371 of SEPHS1 (p.Arg371Trp, p.Arg371Gln, and p.Arg371Gly); seven of these variants were known to be de novo. Structural modeling and biochemical assays were used to understand the effect of these variants on SEPHS1 function. We found that a variant at residue Trp352 results in local structural changes of the C-terminal region of SEPHS1 that decrease the overall thermal stability of the enzyme. In contrast, variants of a solvent-exposed residue Arg371 do not impact enzyme stability and folding but could modulate direct protein-protein interactions of SEPSH1 with cellular factors in promoting cell proliferation and development. In neuronal SH-SY5Y cells, we assessed the impact of SEPHS1 variants on cell proliferation and ROS production and investigated the mRNA expression levels of genes encoding stress-related selenoproteins. Our findings provided evidence that the identified SEPHS1 variants enhance cell proliferation by modulating ROS homeostasis. Our study supports the hypothesis that SEPHS1 plays a critical role during human development and provides a basis for further investigation into the molecular mechanisms employed by SEPHS1. Furthermore, our data suggest that variants in SEPHS1 are associated with a neurodevelopmental disorder.

Treatment-naive and post-treatment glucosylsphingosine (lyso-GL1) levels in a cohort of pediatric patients with Gaucher disease.

Glucosylsphingosine (lyso-GL1) is a biomarker used to monitor disease and treatment response in Gaucher disease. Data from adults show that higher values of lyso-GL1 are associated with increased disease progression, however similar data in the pediatric population is lacking. In a cohort of pediatric patients, we present a relationship between lyso-GL1 value and Gaucher type, age, and treatment response. Data from this study may serve as a reference for providers monitoring children with Gaucher disease.

Newborn Screening for X-Linked Adrenoleukodystrophy: The Initial Illinois Experience.

X-linked adrenoleukodystrophy (X-ALD) is a genetic neurodegenerative disorder with an approximate incidence of 1 in 14,700 births. Both males and females are affected. Approximately one-third of affected males develop childhood cerebral adrenoleukodystrophy, which progresses rapidly to severe disability and death. In these cases, early surveillance and treatment can be lifesaving, but only if initiated before the onset of neurologic symptoms. Therefore, X-ALD was added to the Recommended Uniform Screening Panel. We report outcomes of the initial screening of approximately 276,000 newborns in Illinois. The lipid C26:0 lysophosphatidylcholine (C26:0-LPC) was measured in dried blood spots (DBS) using liquid chromatography with tandem mass spectrometry. Results ≥ 0.28 µmol/L were considered screen positive. Of 18 screen positive results detected, 12 cases were confirmed. Results were reported as borderline if initial and repeat analyses were ≥0.18 and <0.28 µmol/L. Of the 73 borderline screen results, 57 were normal after analysis of a second sample. Five X-ALD cases were identified from borderline screens. Newborn screening of X-ALD was successfully implemented in Illinois, and results were comparable to reports from other states. Early identification of infants with this potentially life-threatening disorder will significantly improve outcomes for these children.

Newborn Screening for Pompe Disease in Illinois: Experience with 684,290 Infants.

Statewide newborn screening for Pompe disease began in Illinois in 2015. As of 30 September 2019, a total of 684,290 infants had been screened and 395 infants (0.06%) were screen positive. A total of 29 cases of Pompe disease were identified (3 infantile, 26 late-onset). While many of the remainder were found to have normal alpha-glucosidase activity on the follow-up testing (234 of 395), other findings included 62 carriers, 39 infants with pseudodeficiency, and eight infants who could not be given a definitive diagnosis due to inconclusive follow-up testing.

Newborn Screening for Mucopolysaccharidosis Type II in Illinois: An Update.

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare, progressive multisystemic lysosomal storage disorder with significant morbidity and premature mortality. Infants with MPS II develop signs and symptoms of the disorder in the early years of life, yet diagnostic delays are very common. Enzyme replacement therapy is an effective treatment option. It has been shown to prolong survival and improve or stabilize many somatic manifestations of the disorder. Our initial experience with newborn screening in 162,000 infants was previously reported. Here, we update that experience with the findings in 339,269 infants. Measurement of iduronate-2-sulfatase (I2S) activity was performed on dried blood spot samples submitted for other newborn screening disorders. A positive screen was defined as I2S activity less than or equal to 10% of the daily median. In this series, 28 infants had a positive screening test result, and four other infants had a borderline result. Three positive diagnoses of MPS II were established, and 25 were diagnosed as having I2S pseudodeficiency. The natural history and the clinical features of MPS II make it an ideal target for newborn screening. Newborn screening was effective in identifying affected infants in our population with an acceptable rate of false positive results.

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease.

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 d5-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.

Population-Based Newborn Screening for Mucopolysaccharidosis Type II in Illinois: The First Year Experience.

OBJECTIVES: To assess the outcome of population-based newborn screening for mucopolysaccharidosis type II (MPS II) during the first year of screening in Illinois. STUDY DESIGN: Tandem mass spectrometry was used to measure iduronate-2-sulfatase (I2S) activity in dried blood spot specimens obtained from 162 000 infant samples sent to the Newborn Screening Laboratory of the Illinois Department of Public Health in Chicago. RESULTS: One case of MPS II and 14 infants with pseudodeficiency for I2S were identified. CONCLUSIONS: Newborn screening for MPS II by measurement of I2S enzyme activity was successfully integrated into the statewide newborn screening program in Illinois.

Peptide ligand-based ELISA reagents for antibody detection.

Detection of specific antibodies has numerous research, therapeutic and diagnostic applications. Short peptide ligands that bind specifically to antibodies with continuous epitopes can be derived from epitope mapping experiments. Short peptide ligands (mimotopes) specific to antibodies with discontinuous epitopes can be identified by screening complex peptide libraries. In an effort to enhance practical utility of such peptide ligands, we describe here a simple approach to turn such target antibody-specific peptide ligands into specific ELISA detection reagents. We show that a simple addition of biotinylated peptide ligands to commonly available horseradish peroxidase (HRP)-labeled streptavidin (or HRP-anti-biotin antibody), or digoxigenin-labeled peptides to HRP-anti-digoxigenin antibody detection reagents transformed these generic detection reagents into sensitive target antibody-specific reagents. ELISA assays performed using these reagents exhibited excellent analytical properties indicating their practical utility for antibody detection. One generic detection reagent can be readily transformed into many different specific ELISA reagents by a simple mix and match design using an appropriate target-specific peptide ligand. Simplicity of preparation of these ELISA reagents for detecting antibodies should facilitate their practical applications.