Huiwen Zhang

Objective: Uniparental disomy (UPD), particularly heterodisomy (hUPD), is an underdiagnosed etiology in cases of fetal growth restriction (FGR) and discordant noninvasive prenatal testing (NIPT). Because conventional absence‐of‐heterozygosity (AOH) analysis frequently misses hUPDs, we aimed to validate a systematic Mendelian inheritance error (MIE) analysis pipeline for trio exome sequencing (trio‐ES) to resolve ambiguous prenatal findings. Method: A two‐stage study analyzed 1948 parent‐offspring trios (postnatal and prenatal samples). A retrospective cohort ( n = 992) established and validated a quantitative biparental inheritance percentage (BPI%) threshold. This workflow was prospectively applied ( n = 956) to evaluate clinical utility, focusing on discordant NIPT and unexplained fetal growth restriction (FGR). Orthogonal analysis of methylation or short‐tandem repeats (STR) were used to confirm identified UPD. Results: Utilizing a BPI% < 0.7 threshold, the pipeline identified 12 clinically significant UPD events. Crucially, 25% (3/12) were hUPDs missed by standard AOH analysis of exome. Prenatally, the pipeline resolved 57.1% (4/7; 95% CI: 18.4%–90.1%) of discordant NIPT cases, inferring trisomy rescue and confined placental mosaicism that explained the associated FGR. Postnatally, it unmasked 8 UPD events associated with imprinting disorders for pediatric cases. Conclusion: MIE analysis of existing trio‐ES data effectively captures hUPDs missed by conventional AOH analysis. Routine integration of this pipeline resolves discordant NIPT results, explains FGR, and enables comprehensive UPD detection.

Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disorder caused by loss‐of‐function variants in the sphingomyelin phosphodiesterase‐1 ( SMPD1 ) gene encoding for the acid sphingomyelinase (ASM). Aberrantly high levels of sphingosylphosphorylcholine (SPC), the deacylated form of sphingomyelin which is the primary accumulated lipid, are key biomarkers in ASMD. The identification of small molecules targeting SPC is an attractive approach for treating ASMD. We screened 1813 Food and Drug Administration‐approved compounds to identify promising candidates that reduce SPC for treating ASMD, using a liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) assay. Eight compounds, floxuridine, dexamethasone, indacaterol maleate, triethylenethiophosphoramide, cytarabine, doramectin, cepharanthine (CEP), and tetrandrine (TE), were identified to abate the accumulation of SPC in ASMD cells. CEP and TE were selected for further pharmacological studies because of their ability to confer the greatest reduction effect on SPC. Finally, a reduction of SPC storage was verified in ASMD lymphoblasts, SMPD1‐ KO cells and SMPD1 ^Y496H fibroblasts by CEP treatment. Additionally, CEP could improve mitochondrial morphology and function, and stimulated lysosome biogenesis by promoting TFEB nuclear translocation in ASMD cells. These results suggest that CEP could potentially be developed as a promising candidate for treating ASMD.

Background: Newborns are referred primary carnitine deficiency (PCD) when a low free carnitine (C0) concentration (<10 μmol/L) is detected, leading to high false-positive referrals. To improve the follow-up protocol for PCD, various acylcarnitines and the summations were comprehensively evaluated in the present study. Methods: A retrospective study was performed using samples due to low C0 concentration. Data were available for 72 patients with genetically confirmed PCD, whereafter C0 with the selected sum of (butyrylcarnitine (C4) + isovalerylcarnitine (C5)) was validated in an additional cohort study including about 80,000 samples. Results: In the discovery study, C4, acetylcarnitine (C2) and C5 exhibited significant discriminant power in distinguishing PCDs from NoPCDs. The area under the ROC curve (AUC) was 99.792% (C4), 98.715% (C2) and 98.620% (C5). The excellent performances in sensitivity, specificity, negative predictive value, positive predictive value (PPV) and accuracy indexes suggested that C4, C2 and C5 would be ideal auxiliary indicators in improving the diagnostic performance of C0 for PCD. Multivariate ROC curve-based exploratory analysis showed that C5, C4 and C2 were the most top-ranked features in differentiating PCDs from NoPCDs. AUC for C4 + C5 was the highest with a cutoff required for 100% sensitivity at 0.181 μmol/L. In the validation cohort, adding C4 + C5 in the NBS program could elevate PPV from 0.75% to 1.54%. Conclusions: Our work revealed that C4 + C5 summation should be used as the auxiliary quantization indicator to reduce false-positive results for PCD.

Background: Newborns are referred primary carnitine deficiency (PCD) when a low free carnitine (C0) concentration (< 10 μmol/L) is detected, leading to high false positive referrals. To improve the follow-up protocol for PCD, various acylcarnitines and the summations were comprehensively evaluated in the present study. Methods: A retrospective study was performed using samples due to low C0 concentration. Data were available for 72 patients with genetically confirmed PCD. Whereafter, C0 with the selected sum of (butyrylcarnitine (C4) + isovalerylcarnitine (C5)) was validated in an additional cohort study including about 80,000 samples. Results: In the discovery study, C4, acetylcarnitine (C2) and C5 exhibited significant discriminant power in distinguishing PCDs from NoPCDs. The area under the ROC curve (AUC) were 99.792% (C4), 98.715% (C2) and 98.620% (C5). The excellent performances in sensitivity, specificity, negative predictive value, positive predictive value (PPV) and accuracy indexes suggested that C4, C2 and C5 would be ideal auxiliary indicators in improving diagnostic performance of C0 for PCD. Multivariate ROC curve based exploratory analysis showed that C5, C4 and C2 were the most top-ranked features in differentiating PCDs from NoPCDs. AUC for C4+C5 was the highest with a cut-off required for 100% sensitivity at 0.181 μmol/L. In the validation cohort, adding C4+C5 in the NBS program could elevate PPV from 0.75% to 1.54%. Conclusions: Our work revealed that C4+C5 summation should be as the auxiliary quantization indicator to reduce false-positive results for PCD.

Niemann-Pick disease type C (NPC) is a rare, autosomal recessive, neurodegenerative disease associated with a wide variety of progressive neurological manifestations. Miglustat has demonstrated efficacy to delay progressive neurological deterioration in patients with NPC. We conducted a multicenter, open-label, single-arm, phase IV, post-approval commitment study to evaluate the efficacy and safety of miglustat among Chinese patients with NPC. Eligible patients were aged ≥ 4 years with an established diagnosis of NPC with two type C1 or C2 pathogenic markers or one marker with a positive biomarker (oxysterol, lysosphingolipids, or bile acids) and high clinical suspicion of NPC. Patients received oral miglustat ranging from 100 mg twice daily to 200 mg three times daily. The primary outcome was change in horizontal saccadic eye movement parameters from baseline to week 52. Seventeen patients were enrolled (median age: 14.0 years). From baseline to week 52, mean saccadic peak acceleration and velocity increased by 19.2% and 12.5%, respectively, while mean peak duration and linear regression decreased by 6.5% and 15.6%, respectively. By week 52, ambulation, manipulation, language, swallowing, and ocular movements had improved or stabilized versus baseline. All patients experienced treatment-emergent adverse events (TEAEs). Treatment-related TEAEs were reported in 12 patients with the most common being diarrhea (n = 12). Two patients died due to accidental death and asphyxia unrelated to miglustat treatment. This study demonstrated disease stabilization in Chinese patients with NPC receiving miglustat. Safety findings were consistent with miglustat's known safety profile. The study was registered at ClinicalTrials.gov (NCT03910621).

Background: Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disease caused by biallelic variants in the N-acetylgalactosamine-6-sulfatase (GALNS) gene and is characterized by progressive and multi-system involvements, dominantly with skeletal deformities. A mild form of MPS IVA often presents with atypical symptoms and can go unrecognized for years. Methods: The diagnosis of MPS IVA was confirmed via GALNS enzyme activity testing in leukocytes. Clinical features were collected. Molecular analysis was performed by next generation sequence and Sanger sequencing of the GALNS gene. The pathogenicity of the deep intron variant was verified by mRNA analyses. Results: Thirteen patients with mild MPS IVA from six families were included. All probands first visit pediatric orthopedists and it took 5.6 years to be diagnosed after the disease onset. The most common symptoms in our series were waddling gait (85%), short neck (69%) and flat feet (62%). Radiologic findings indicated skeletal abnormalities in all patients, especially modification of the vertebral bodies (100%) and acetabular and femoral head dysplasia (100%). Five novel GALNS variants, including c.121-2_121-1insTTTGCTGGCATATGCA, E2 deletion, c.569 A > G, c.898 + 2 T > A, and c.1139 + 2 T > C, were identified. The most common variant, a deep intron variant NM_000512.5: c.121–210 C > T (NM_001323544.2: c.129 C > T, p.G43G), was revealed to result in an 11 bp deletion (c.128_138delGCGATGCTGAG, p.Gly43Aspfs*5) on GALNS mRNA in the GALNS transcript of NM_001323544.2. Conclusions: This study provides significant insights into the clinical features and molecular characteristics that contribute to the early diagnosis of mild MPS IVA. On the basis of our cohort, orthopedists need to be able to recognize signs and symptoms of mild MPS IVA as well as the molecular and biochemical diagnosis so that an early diagnosis and treatment can be instituted.

Lysosomal storage disorders (LSDs) make up a group of inborn organelle disorders caused by the deficiency of specific lysosomal enzymes or transport proteins, resulting in increased accumulation of macromolecules and lysosomal dysfunction.^1,2 LSDs comprise nearly 60 distinct disease entities, most of which have autosomal recessive inheritance but a few of which have X-linked inheritance, including Fabry disease and mucopolysaccharidosis type II.^3,4 The combined incidence of LSDs is estimated to be 1 in 4000 to 1 in 9000 live births according to a 2022 report by the American College of Medical Genetics and Genomics (ACMG).⁵ LSDs can affect multiple organs, especially the central nervous system, and patients who are untreated may be at risk of lifelong disability or even death.⁶ Treatment options for LSDs include enzyme replacement therapy, hematopoietic stem cell transplantation, and substrate reduction therapy.^7,8 Early diagnosis and treatment initiation are essential for reducing disease-related morbidity and mortality.

Hundreds of NPC1 variants cause highly heterogeneous phenotypes. This study aims to explore the genotype-phenotype correlation of NPC1, especially for missense variants. In a well-characterized cohort, phenotypes are graded into three clinical forms: mild, intermediate, and severe. Missense residue structural location was stratified into three categories: surface, partially, and fully buried. The association of phenotypes with the topography of the amino acid substitution in the protein structure was investigated in our cohort and validated in two reported cohorts. One hundred six unrelated NPC1 patients were enrolled. A significant correlation of genotype-phenotype was found in 81 classified individuals with two or one (the second was null variant) missense variant (p < 0.001): of 25 patients with at least one missense variant of surface (group A), 19 (76%) mild, six (24%) intermediate, and none severe; of 31 cases with at least one missense variant of partially buried without surface variants (group B), 11 (35%) mild, 16 (52%) intermediate, and four (13%) severe; of the remaining 25 patients with two or one buried missense variants (group C), eight (32%) mild, nine (36%) intermediate, and eight (32%) severe. Additionally, 7-ketocholesterol, the biomarker, was lower in group A than in group B (p = 0.024) and group C (p = 0.029). A model was proposed that accurately predicted phenotypes of 72 of 90 (80%), 73 of85 (86%), and 64 of 69 (93%) patients in our cohort, Italian, and UK cohort, respectively. This study proposed a novel genotype-phenotype correlation in NPC1, linking the underlying molecular pathophysiology with clinical phenotype and aiding genetic counseling and evaluation in clinical practice.