Single-cell metabolomics in rare disease: From technology to disease.

With the development of clinical experience and technology, rare diseases (RDs) are gradually coming into the limelight. As they often lead to poor prognosis, it is urgent to promote the accuracy and rapidity of diagnosis and promote the development of therapeutic drugs. In recent years, with the rapid improvement of single-cell sequencing technology, the advantages of multi-omics combined application in diseases have been continuously explored. Single-cell metabolomics represents a powerful tool for advancing our understanding of rare diseases, particularly metabolic RDs, and transforming clinical practice. By unraveling the intricacies of cellular metabolism at a single-cell resolution, this innovative approach holds the potential to revolutionize diagnosis, treatment, and management strategies, ultimately improving outcomes for RDs patients. Continued research and technological advancements in single-cell metabolomics are essential for realizing its full potential in the field of RDs diagnosis and therapeutics. It is expected that single-cell metabolomics can be better applied to RDs research in the future, for the benefit of patients and society.

Inherited metabolic disorders in Cyprus.

Selective screening for inherited metabolic disorders (IMD) began in Cyprus in 1990. Over the last thirty-three years 7388 patients were investigated for IMD and 200 diagnoses were made (diagnostic yield 2.7%). The existence of a single laboratory of Biochemical Genetics for the whole island facilitated the creation of a national registry for IMD. The minimal prevalence of IMD in Cyprus is 53.3 cases per 100,000 live births. The most common group are disorders of amino acid metabolism (41.0%), followed by disorders of carbohydrate metabolism (16.5%), disorders of complex molecule degradation (16.5%), mitochondrial disorders (10.5%) and disorders of vitamin and co-factor metabolism (5.5%). Hyperphenylalaninaemia is the most common IMD (14.0%) followed by galactosaemia (7.0%), glutaric aciduria type I (5.5%) and MSUD (4.0%). Some disorders were found to have a relatively high incidence in specific communities, for example Sandhoff disease among the Cypriot Maronites and GM1 gangliosidosis in one particular area of the island. Other disorders were found to have a relatively higher overall incidence, compared to other Caucasian populations, for example galactosaemia, glutaric aciduria type I and MSUD, while fatty acid oxidation defects, Gaucher disease and classic PKU were found to have a relatively lower incidence. Molecular characterization of selected disorders revealed many novel genetic variants, specific to the Cypriot population.

Pediatric palliative care for metabolic diseases: 20-year epidemiological survey of outpatients at a Brazilian quaternary hospital.

The interface between pediatric palliative care (PPC) and inborn metabolic diseases (IMD) remains incipient, though these conditions fill the state of art of complex chronic diseases, eligible to this health approach. We analyzed the medical records of PPC clinic during the years 2001 to 2021 and the IMD outpatients. We established a parallel with the world scientific literature concerning the epidemiology of PPC and IMD. Among outpatients, 14% were diagnosed with IMD, which were referred to the PPC service earlier compared to Non-IMD cases. The Group 3 (complex molecules) was the most frequent (64.7%), following by Group 1 representing by small molecules (21.6%), the latter having a lower median age at diagnosis when compared to the former (0.7 vs. 5.2 years, p = 0.001). The sphingolipidoses were the pathologies most frequent in our cohort, in line with what was observed in the literature. There were no differences between IMD groups in terms of diagnosis and PPC referral age, however in Non-IMD conditions, the age of diagnosis were earlier than IMD. Nevertheless, IMD group showed lower age of referral to PPC. The IMD comprises large fraction of outpatients in the PPC setting, thus further studies are needed in this field.

CAD-Related Disorder (EIEE-50) in an Infant With Cortical Visual Impairment.

PURPOSE: To document the association of CAD-related disorder (EIEE-50) with cortical visual impairment. OBSERVATIONS: An 8-month-old Caucasian boy with whole genome sequencing confirming 2 variants in the gene CAD, who presented with severe seizures, microcephaly, hyperreflexia, hypotonia, anemia, and severe cortical visual impairment. Magnetic resonance imaging (MRI) of the brain noted thickened cortical gray matter along the right calcarine fissure as well as changes suggesting malformation of cortical development. Empiric uridine monophosphate supplementation has significantly improved seizure activity, hypotonia, and development and has led to resolution of anemia. CONCLUSIONS AND IMPORTANCE: CAD-related disorder is treatable and may affect visual cortical development causing severe secondary cortical visual impairment, a newly described clinical manifestation.

Elevated C5-hydroxy acylcarnitine in an infant girl as a result of holocarboxylase synthetase deficiency.

CONTEXT: Elevated 3-hydroxyisovaleryl-/2-methyl-3-hydroxybutyryl (C5-OH) acylcarnitine in blood can result from several genetic enzyme deficiencies: 3-methylcrotonyl CoA carboxylase deficiency, 3-hydroxy 3-methylglutaryl-CoA lyase deficiency, beta-ketothiolase deficiency, 2-methyl 3-hydroxybutyryl-CoA dehydrogenase deficiency, primary 3-methylglutaconic aciduria, multiple biotin-dependent carboxylase deficiencies and biotin metabolism disorders. Biochemical tests help differentiate these causes while molecular tests are usually required for definitive diagnosis. CASE DESCRIPTION: We reported an infant girl with newborn screen findings of elevated C5-OH acylcarnitine. She had further confirmational biochemical testing including plasma acylcarnitines, urine organic acids and urine acylglycines. Patient's urine organic acid profile showed markedly increased 3-hydroxyisovaleric acid and 3-methylcrotonylglycine. Urine acylglycine test reported a large increase of 3-methylcrotonylglycine and plasma acylcarnitine test repeated the finding of elevated C5-OH acylcarnitine together with propionyl acylcarnitine elevation. These results point to multiple biotin-dependent carboxylase deficiency. Molecular tests revealed a homozygous mutation in the holocarboxylase synthetase gene that is consistent with her biochemical test findings. This case demonstrated the critical role of newborn screen in identifying inborn errors of metabolism that may otherwise be missed and lead to severe morbidity later in life. It also showcased that both biochemical and molecular tests are essential tools in the diagnosis.

Neurofilament light chain as a biomarker for acute hepatic porphyrias.

Background: Acute hepatic porphyrias (AHP) represent a rare group of inherited metabolic disorders of heme biosynthesis pathway. This study aims to determine the diagnostic and prognostic value of serum neurofilament light chain (NfL) as potential biomarker for AHP. Methods: We conducted a cross-sectional observational study to evaluate NfL levels in patients with AHP. They were divided in different groups: normal health individuals; patients with definitive diagnosis of AHP during acute episodes; patients with AHP and infrequent attacks; patients with AHP and recurrent attacks; asymptomatic individuals with positive genetic testing and urinary delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) levels elevated 4 or more times ("high excretors"); asymptomatic individuals with exclusive positive genetic test; control group with Hereditary Amyloidosis related to Transthyretin with Polyneuropathy (ATTRv-PN). Results: During acute attacks, serum NfL levels were 68 times higher compared to normal controls and disclosed a strong correlation with ALA and PBG levels; also exhibited elevated levels in patients with chronic symptoms regardless of the number of disease attacks compared to healthy controls, and at similar levels to patients with ATTRv-PN, which is a model of progressive neuropathy. Conclusion: This study represents the first to establish NfL as a biomarker for AHP, disclosing NfL as a sensitive biomarker for axonal damage and chronic symptom occurrence. This study not only underscores that neurological damage associated with the disease in any patient, irrespective of the number of attacks, but also reinforces the progressive and profoundly debilitating nature of acute and chronic symptoms observed in individuals with AHP.

206,977 newborn screening results reveal the ethnic differences in the spectrum of inborn errors of metabolism in Huaihua, China.

Background: Inborn errors of metabolism (IEMs) are rare diseases caused by inherited defects in various biochemical pathways that strongly correlate with early neonatal mortality and stunting. Currently, no studies have reported on the incidence of IEMs of multi-ethnic groups in Huaihua, China. Methods: A total of 206,977 neonates with self-reported ethnicity who underwent IEM screening at Huaihua from 2015 to 2021 were selected for observation. Among them, 69 suspected IEM-positive neonates were referred for urine gas chromatography-mass spectrometry analysis, biochemical detection, next-generation sequencing, and Sanger sequencing. Results: Sixty-nine newborns were diagnosed with IEMs, with an overall incidence of 1:3,000. The two most common disorders were 2-methylbutyryl glycinuria (1:7,137) and phenylalanine hydroxylase deficiency (1:22,997). Moreover, the incidence of IEMs in the minority ethnic group (Miao, Dong, Tujia and Yao) (1:1,852) was markedly higher than in the Han ethnic group (1:4,741). Some ethnic features variants were identified; NM_001609.4:c.1165A>G in the ACADSB gene for Miao and Dong ethnic groups, NM_014251.2:c.852_855del in the SLC25A13 gene for Miao ethnic groups. Conclusion: This study revealed the IEM incidence within the minority ethnic groups is markedly higher than among the Han nationality and the gene variant spectrum is dramatically different in Huaihua, China. Hence, It serves as a theoretical reference for the screening and diagnosing of neonatal IEMs of multi-ethnic groups in the Huaihua area, and across China.

Establishment of Age Specific Reference Interval for Aminoacids and Acylcarnitine in Dried Blood Spot by Tandem Mass Spectrometry.

The Extended Screening for Inborn Errors of Metabolism is done for aminoacidopathies, fatty acid oxidation disorders and organic acid disorders. In a single dried blood spot, the tandem mass spectrometry is capable of measuring multiple analytes like amino acids, acylcarnitines, nucleosides, succinylacetone and lysophosphatidylcholines. This study was proposed to establish age specific reference internal for aminoacids and acylcartinitine in dried blood spot by tandem mass spectrometry. A total of 480 apparently healthy children were enrolled for the study and sub classified into four groups as follows: Group A: 0-1 month, Group B: 1 month-1 year, Group C: 1-5 year and Group D: 5-12 years each having 120 participants. Sample size were calculated as per CLSI approved guidelines. Tables 1 and 2 presents the age-specific percentile distribution of aminoacids and acylcarnitines established from healthy subjects as per rank-based method recommended by the IFCC and CLSI. Tables 3, 4 and 5 presents the cut-off values of primary and secondary marker/ratios for screening of aminoacidopathies, fatty acid oxidation disorders and organic acid disorders respectively. As a general principle, the interpretation of extended newborn screening results should be based on age specific cut-off established by the laboratory for primary analyte concentration and secondary analyte concentration/ ratios. This study was useful in establishing age specific cut-off values for various amino acids and acylcarnitines in South Indian population. [Table: see text] [Table: see text] [Table: see text] [Table: see text] [Table: see text].

Newborn Screening for Inborn Errors of Metabolism by Next-Generation Sequencing Combined with Tandem Mass Spectrometry.

The aim of this study was to observe the outcomes of newborn screening (NBS) in a certain population by using next-generation sequencing (NGS) as a first-tier screening test combined with tandem mass spectrometry (MS/MS). We performed a multicenter study of 29,601 newborns from eight screening centers with NBS via NGS combined with MS/MS. A custom-designed panel targeting the coding region of the 142 genes of 128 inborn errors of metabolism (IEMs) was applied as a first-tier screening test, and expanded NBS using MS/MS was executed simultaneously. In total, 52 genes associated with the 38 IEMs screened by MS/MS were analyzed. The NBS performance of these two methods was analyzed and compared respectively. A total of 23 IEMs were diagnosed via NGS combined with MS/MS. The incidence of IEMs was approximately 1 in 1287. Within separate statistical analyses, the positive predictive value (PPV) for MS/MS was 5.29%, and the sensitivity was 91.3%. However, for genetic screening alone, the PPV for NGS was 70.83%, with 73.91% sensitivity. The three most common IEMs were methylmalonic academia (MMA), primary carnitine deficiency (PCD) and phenylketonuria (PKU). The five genes with the most common carrier frequencies were PAH (1:42), PRODH (1:51), MMACHC (1:52), SLC25A13 (1:55) and SLC22A5 (1:63). Our study showed that NBS combined with NGS and MS/MS improves the performance of screening methods, optimizes the process, and provides accurate diagnoses.

Psychiatric Manifestations in Children and Adolescents with Inherited Metabolic Diseases.

Background: Inherited metabolic disorders (IEMs) can be represented in children and adolescents by psychiatric disorders. The early diagnosis of IEMs is crucial for clinical outcome and treatment. The aim of this review is to analyze the most recurrent and specific psychiatric features related to IEMs in pediatrics, based on the onset type and psychiatric phenotypes. Methods: Following the PRISMA Statement, a systematic literature review was performed using a predefined algorithm to find suitable publications in scientific databases of interest. After removing duplicates and screening titles and abstracts, suitable papers were analyzed and screened for inclusion and exclusion criteria. Finally, the data of interest were retrieved from the remaining articles. Results: The results of this study are reported by type of symptoms onset (acute and chronic) and by possible psychiatric features related to IEMs. Psychiatric phenomenology has been grouped into five main clinical manifestations: mood and anxiety disorders; schizophrenia-spectrum disorders; catatonia; eating disorders; and self-injurious behaviors. Conclusions: The inclusion of a variety of psychiatric manifestations in children and adolescents with different IEMs is a key strength of this study, which allowed us to explore the facets of seemingly different disorders in depth, avoiding possible misdiagnoses, with the related delay of early and appropriate treatments.

Improving access to gene therapy for rare diseases.

Effective gene therapy approaches have been developed for many rare diseases, including inborn errors of immunity and metabolism, haemoglobinopathies and inherited blindness. Despite successful pre-clinical and clinical results, these gene therapies are not widely available, primarily for non-medical reasons. Lack of commercial interest in therapies for ultra-rare diseases, costs of development and complex manufacturing processes required for advanced therapy medicinal products (ATMPs) are some of the main problems that are restricting access. The complexities and costs of navigating the regulatory environments in different jurisdictions for treatments that affect small numbers of patients is a problem unique to ATMPS for rare and ultra-rare diseases. In this Perspective, we outline some of the challenges and potential solutions that, we hope, will improve access to gene therapy for rare diseases.

Decimocuarta lección Jesús Culebras. Dieta cetogénica, un tratamiento a medio descubrir / Fourteenth Jesús Culebras Lecture. Ketogenic diet, a half-discovered treatment

La dieta cetogénica constituyó desde su inicio un planteamiento sorprendente para el tratamiento de la epilepsia. Someter al organismo a un cambio en la obtención de energía, pasando de depender de los carbohidratos a hacerlo de las grasas, pone en marcha toda una serie de rutas bioquímicas que, de forma independiente pero también complementaria, dan lugar a un conjunto de efectos que benefician al paciente. Esta búsqueda de su mecanismo de acción, de idear cómo mejorar el cumplimiento y de aprovecharla para otras enfermedades ha marcado su trayectoria. En este artículo se revisan someramente estos aspectos, haciendo hincapié en la importancia de seguir realizando investigación básica y clínica para que este tratamiento pueda aplicarse con bases científicas sólidas.(AU)

The ketogenic diet was an amazing approach to treating epilepsy from its beginning. The body undergoes a change in obtaining energy, going from depending on carbohydrates to depending on fats, and then a whole series of biochemical routes are launched that, independently but also complementary, give rise to a set of effects that benefit the patient. This search for its mechanism of action, of devising how to improve compliance and take advantage of it for other diseases has marked its trajectory. This article briefl y reviews these aspects, emphasizing the importance of continuing to carry out basic and clinical research so that this treatment can be applied with solid scientific bases.(AU)

Comparative analysis of inherited metabolic diseases in normal newborns and high-risk children: Insights from a 10-year study in Shanghai.

BACKGROUND: Compare the differences between normal newborns and high-risk children with inherited metabolic diseases. The disease profile includes amino acidemias, fatty acid oxidation disorders, and organic acidemias. METHODS: Data was collected on newborns and children from high-risk populations in Shanghai from December 2010 to December 2020. RESULTS: 232,561 newborns were screened for disorders of organic, amino acid, and fatty acid metabolism. The initial positive rate was 0.66 % (1,526/232,561) and the positive recall rate was 77.85 %. The positive predictive value is 4.71 %. Among them, 56 cases were diagnosed as metabolic abnormalities. The total incidence rate is 1:4153. Hyperphenylalaninemia and short-chain acyl-CoA dehydrogenase are the most common diseases in newborns. In addition, in 56 children, 39 (69.42 %) were diagnosed by genetic sequencing. Some hotspot mutations in 14 IEMs have been observed, including PAH gene c.728G > A, c.611A > G, and ACADS gene c. 1031A > G, c.164C > T. A total of 49,860 symptomatic patients were screened, of which 185 were diagnosed with IEM, with a detection rate of 0.37 %. The most commonly diagnosed diseases in high-risk infants aremethylmalonic acidemia and hyperphenylalaninemia. CONCLUSION: There are more clinical cases of congenital metabolic errors diagnosed by tandem mass spectrometry than newborn screening. The spectrum of diseases, prevalence, and genetic characteristics of normal newborns and high-risk children are quite different.

Gyrate atrophy of the choroid and retina: Update on diagnosis and treatment.

Gyrate atrophy of the choroid and retina (GACR) is a rare autosomal recessive disease characterised by elevated plasma ornithine levels due to deficiency of the enzyme ornithine aminotransferase (OAT). The accumulation of this amino acid in plasma leads to the development of patches of chorioretinal atrophy in the peripheral retina extending into the macular area. Patients usually present with night blindness followed by constriction of the visual field and, finally, decreased central vision and blindness. The disease is diagnosed by the presence of the characteristic clinical picture, the presence of hyperornithinaemia in plasma and the detection of mutations in the OAT enzyme gene. There is currently no effective gene therapy and the most common therapeutic intervention mainly involves dietary modifications with arginine restriction. This article aims to summarise the pathogenesis, clinical and diagnostic findings and treatment options in patients with GACR.

Targeted ultra performance liquid chromatography tandem mass spectrometry procedures for the diagnosis of inborn errors of metabolism: validation through ERNDIM external quality assessment schemes.

OBJECTIVES: Early diagnosis of inborn errors of metabolism (IEM) is crucial to ensure early detection of conditions which are treatable. This study reports on targeted metabolomic procedures for the diagnosis of IEM of amino acids, acylcarnitines, creatine/guanidinoacetate, purines/pyrimidines and oligosaccharides, and describes its validation through external quality assessment schemes (EQA). METHODS: Analysis was performed on a Waters ACQUITY UPLC H-class system coupled to a Waters Xevo triple-quadrupole (TQD) mass spectrometer, operating in both positive and negative electrospray ionization mode. Chromatographic separation was performed on a CORTECS C18 column (2.1 × 150, 1.6 µm). Data were collected by multiple reaction monitoring. RESULTS: The internal and EQA results were generally adequate, with a few exceptions. We calculated the relative measurement error (RME) and only a few metabolites displayed a RME higher than 30 % (asparagine and some acylcarnitine species). For oligosaccharides, semi-quantitative analysis of an educational panel clearly identified the 8 different diseases included. CONCLUSIONS: Overall, we have validated our analytical system through an external quality control assessment. This validation will contribute to harmonization between laboratories, thus improving identification and management of patients with IEM.

When rare meets common: Treatable genetic diseases are enriched in the general psychiatric population.

Mental illnesses are one of the biggest contributors to the global disease burden. Despite the increased recognition, diagnosis and ongoing research of mental health disorders, the etiology and underlying molecular mechanisms of these disorders are yet to be fully elucidated. Moreover, despite many treatment options available, a large subset of the psychiatric patient population is nonresponsive to standard medications and therapies. There has not been a comprehensive study to date examining the burden and impact of treatable genetic disorders (TGDs) that can present with neuropsychiatric features in psychiatric patient populations. In this study, we test the hypothesis that TGDs that present with psychiatric symptoms are more prevalent within psychiatric patient populations compared to the general population by performing targeted next-generation sequencing of 129 genes associated with 108 TGDs in a cohort of 2301 psychiatric patients. In total, 48 putative affected and 180 putative carriers for TGDs were identified, with known or likely pathogenic variants in 79 genes. Despite screening for only 108 genetic disorders, this study showed a two-fold (2.09%) enrichment for genetic disorders within the psychiatric population relative to the estimated 1% cumulative prevalence of all single gene disorders globally. This strongly suggests that the prevalence of these, and most likely all, genetic diseases is greatly underestimated in psychiatric populations. Increasing awareness and ensuring accurate diagnosis of TGDs will open new avenues to targeted treatment for a subset of psychiatric patients.

The evaluation of inherited metabolic diseases presenting with rhabdomyolysis from Turkey: Single center experience.

Aim: It was aimed to identify markers that would indicate which cases presenting with rhabdomyolysis are more likely to be associated with inherited metabolic diseases. Methods: We analyzed 327 children who applied to our Hospital Pediatric Nutrition and Metabolic Diseases Clinic with rhabdomyolysis. The diagnosis of rhabdomyolysis was made by measuring the serum creatinine kinase level in cases presenting with muscle pain, weakness and dark urine. Results: Metabolic disease was detected in 29 (16/13, M/F) patients from 26 different families. 298 patients (165/133, M/F) had normal metabolic work-up. We detected glutaric aciduria type 2 in 13 patients (44,6%), glycogen storage disease type 5 in three patients (10,3%), MCAD deficiency in three patients(10,3%), mitochondrial disease in three patients (10,3%), glycogen storage disease type 9 in one patient (3,5%), VLCAD deficiency in one patient (3,5%), LCHAD deficiency in one patient (3,5%), CPT2 deficiency in one patient(3,5%), Tango2 deficiency in one patient (3,5%), lipin-1 deficiency in one patient (3,5%) and primary carnitine deficiency in one patient (3,5%). Conclusion: In our study, consanguineous marriage, developmental delay, and intellectual disability were found more frequently in patients with metabolic disease. In addition, CK levels above 2610 U/L was found to be significantly correlated with metabolic disease.

What should rheumatologists know about Gaucher disease and Fabry disease? Connecting the dots for an overview.

Gaucher and Fabry diseases are lysosomal storage disorders in which deficient enzyme activity leads to pathological accumulation of sphingolipids. These diseases have a broad phenotypic presentation. Musculoskeletal symptoms and pain complaints are frequently reported by patients. Thus, rheumatologists can be contacted by these patients, contributing to the correct diagnosis, earlier indication of appropriate treatment and improvement of their prognosis. This review describes important concepts about Gaucher and Fabry diseases that rheumatologists should understand to improve patients' quality of life and change the natural history of these diseases.

Importance of genetic sequencing studies in managing chronic neonatal diarrhea: a case report of a novel variant in the glucose-galactose transporter SLC5A1.

Introduction: Congenital glucose-galactose malabsorption (CGGM) is a rare autosomal recessive disorder that primarily causes chronic intractable diarrhea. This study aims to describe the clinical history, laboratory profile, diagnostic workflow, and management of the first patient reported with CGGM in Mexico. Methods: The case involves a Mexican female infant with recurrent admissions to the emergency room since birth due to chronic diarrhea. Results: The infant was born at term by C-section with a birth weight of 3.120 kg and height of 48 cm for consanguineous parents. She had been breastfed until day 5 of her life when she presented lethargy, diarrhea, abdominal discomfort, and jaundice. During the first evaluation at the emergency room, the significant laboratory finding was blood tyrosine elevation; afterward, amino acid and succinylacetone determinations were obtained, discarding tyrosinemia. When admitted to the hospital, an abdominal ultrasound detected a duplex collecting system. At this time, rice formula was introduced to the patient. She was discharged with jaundice improvement, but diarrhea persisted. Several formula changes had been made from rice to extensively hydrolyzed casein protein to whey-based, with no clinical improvement; the patient still had 10-12 excretions daily. In the second hospitalization, the patient presented anemia, severe dehydration, hyperammonemia, and renal tubular acidosis. A next-generation sequencing panel for inborn errors of metabolism and congenital diarrhea was performed, identifying a homozygous variant in SLC5A1 (c.1667T > C). The diagnosis of CGGM was made at 3 months of age. The infant was initially treated with a modular galactose-glucose-free formula with oil, fructose, casein, minerals, and vitamins until a commercial fructose-based formula was introduced. This led to a complete resolution of diarrhea and improved nutritional status. Discussion: Diagnosing CGGM is challenging for clinicians, and next-generation sequencing is a valuable tool for providing appropriate treatment. More detailed information on patients with this condition might lead to possible phenotype-genotype correlations. This case's primary clinical and biochemical findings were chronic diarrhea, anemia, jaundice, renal tubular acidosis, hyperammonemia, and initial hypertyrosinemia. Symptoms were resolved entirely with the fructose-based formula.