Validity and reliability of the MetabQoL 1.0 and assessment of neuropsychiatric burden in organic acidemias: Reflections from Turkey.

OBJECTIVES: The MetabQoL 1.0 is the first disease-specific health related quality of life (HrQoL) questionnaire for patients with intoxication-type inherited metabolic disorders. Our aim was to assess the validity and reliability of the MetabQoL 1.0, and to investigate neuropsychiatric burden in our patient population. METHODS: Data from 29 patients followed at a single center, aged between 8 and 18 years with the diagnosis of methylmalonic acidemia (MMA), propionic acidemia (PA) or isovaleric acidemia (IVA), and their parents were included. The Pediatric Quality of Life Inventory (PedsQoL) was used to evaluate the validity and reliability of MetabQoL 1.0. RESULTS: The MetabQoL 1.0 was shown to be valid and reliable (Cronbach's alpha: 0.64-0.9). Fourteen out of the 22 patients (63.6%) formally evaluated had neurological findings. Of note, 17 out of 20 patients (85%) had a psychiatric disorder when evaluated formally by a child and adolescent psychiatrist. The median mental scores of the MetabQoL 1.0 proxy report were significantly higher than those of the self report (p = 0.023). Patients with neonatal-onset disease had higher MetabQoL 1.0 proxy physical (p = 0.008), mental (p = 0.042), total scores (p = 0.022); and self report social (p = 0.007) and total scores (p = 0.043) than those with later onset disease. CONCLUSIONS: This study continues to prove that the MetabQoL 1.0 is an effective tool to measure what matters in intoxication-type inherited metabolic disorders. Our results highlight the importance of clinical assessment complemented by patient reported outcomes which further expands the evaluation toolbox of inherited metabolic diseases.

Clinical, biochemical, and molecular insights into Cerebrotendinous Xanthomatosis: A nationwide study of 100 Turkish individuals.

OBJECTIVE: Cerebrotendinous xanthomatosis (CTX) is an inherited metabolic disorder characterized by progressive neurologic and extraneurologic findings. The aim of this retrospective, descriptive study was to explore the time of presentation and diagnosis, and to expand the phenotype and genotype of CTX, based on a nationwide and comprehensive series of patients in Turkey. METHODS: The demographic, clinical, biochemical and genotypic characteristics of the CTX patients were reviewed. Data on molecular analysis, age of onset and diagnosis, diagnostic delay, neurologic and extraneurologic symptomatology, results of plasma cholestanol levels, brain magnetic resonance imaging and electromyography at the time of diagnosis were reviewed. RESULTS: 100 confirmed CTX patients from 72 families were included. The mean age at diagnosis was 28.16 ± 14.28 years, and diagnostic delay was 18.39 ± 13.71 years. 36 patients were diagnosed in childhood. Frequency of intention tremor (p = 0.069), peripheral neuropathy (p = 0.234) and psychiatric manifestations (p = 0.396) did not differ between two groups, demonstrating the high rate in pediatric patients. Three adult patients showed a milder phenotype without neurologic involvement. Seven patients had normal plasma cholestanol levels despite neurological impairment. Sequencing of the CYP27A1 gene revealed 25 different variants, with a novel c.671_672del variant not previously described in literature. CONCLUSION: Based on the observations of this Turkish CTX cohort, it is emphasized that the true prevalence of CTX is probably underestimated and that it has a wide spectrum of clinical phenotypes even without neurological impairment. In children, abnormal cerebellar findings, peripheral neuropathy and psychiatric findings associated with intellectual disability have been suggested as warning signs to avoid diagnostic delay. In cases of clinical suspicion, molecular analysis is recommended despite normal plasma cholestanol levels, as severe neurologic involvement may occur in CTX patients without elevated cholestanol levels.

Impact of citrulline substitution on clinical outcome after liver transplantation in carbamoyl phosphate synthetase 1 and ornithine transcarbamylase deficiency.

Carbamoyl phosphate synthetase 1 (CPS1) and ornithine transcarbamylase (OTC) deficiencies are rare urea cycle disorders, which can lead to life-threatening hyperammonemia. Liver transplantation (LT) provides a cure and offers an alternative to medical treatment and life-long dietary restrictions with permanent impending risk of hyperammonemia. Nevertheless, in most patients, metabolic aberrations persist after LT, especially low plasma citrulline levels, with questionable clinical impact. So far, little is known about these alterations and there is no consensus, whether l-citrulline substitution after LT improves patients' symptoms and outcomes. In this multicentre, retrospective, observational study of 24 patients who underwent LT for CPS1 (n = 11) or OTC (n = 13) deficiency, 25% did not receive l-citrulline or arginine substitution. Correlation analysis revealed no correlation between substitution dosage and citrulline levels (CPS1, p = 0.8 and OTC, p = 1). Arginine levels after liver transplantation were normal after LT independent of citrulline substitution. Native liver survival had no impact on mental impairment (p = 0.67). Regression analysis showed no correlation between l-citrulline substitution and failure to thrive (p = 0.611) or neurological outcome (p = 0.701). Peak ammonia had a significant effect on mental impairment (p = 0.017). Peak plasma ammonia levels correlate with mental impairment after LT in CPS1 and OTC deficiency. Growth and intellectual impairment after LT are not significantly associated with l-citrulline substitution.

The continuously evolving phenotype of succinic semialdehyde dehydrogenase deficiency.

The objective of the study is to evaluate the evolving phenotype and genetic spectrum of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD) in long-term follow-up. Longitudinal clinical and biochemical data of 22 pediatric and 9 adult individuals with SSADHD from the patient registry of the International Working Group on Neurotransmitter related Disorders (iNTD) were studied with in silico analyses, pathogenicity scores and molecular modeling of ALDH5A1 variants. Leading initial symptoms, with onset in infancy, were developmental delay and hypotonia. Year of birth and specific initial symptoms influenced the diagnostic delay. Clinical phenotype of 26 individuals (median 12 years, range 1.8-33.4 years) showed a diversifying course in follow-up: 77% behavioral problems, 76% coordination problems, 73% speech disorders, 58% epileptic seizures and 40% movement disorders. After ataxia, dystonia (19%), chorea (11%) and hypokinesia (15%) were the most frequent movement disorders. Involvement of the dentate nucleus in brain imaging was observed together with movement disorders or coordination problems. Short attention span (78.6%) and distractibility (71.4%) were the most frequently behavior traits mentioned by parents while impulsiveness, problems communicating wishes or needs and compulsive behavior were addressed as strongly interfering with family life. Treatment was mainly aimed to control epileptic seizures and psychiatric symptoms. Four new pathogenic variants were identified. In silico scoring system, protein activity and pathogenicity score revealed a high correlation. A genotype/phenotype correlation was not observed, even in siblings. This study presents the diversifying characteristics of disease phenotype during the disease course, highlighting movement disorders, widens the knowledge on the genotypic spectrum of SSADHD and emphasizes a reliable application of in silico approaches.

Predictors of eventual requirement of phenylalanine-restricted diet in young infants with phenylalanine hydroxylase deficiency initially managed with sapropterin monotherapy.

BACKGROUND: Phenylalanine (Phe)-restricted diet is associated with lower quality of life for patients with phenylketonuria (PKU), and a concern for caregivers of recently-diagnosed infants. Sapropterin is an oral drug used as an alternative or adjunct to dietary treatment. We have observed that some of the young infants initially managed successfully with sapropterin monotherapy have required dietary treatment in long-term follow-up. We aimed to determine the baseline factors associated with future initiation of dietary treatment in these patients. METHODS: Data were obtained retrospectively from the medical records of 80 PKU patients started on sapropterin monotherapy before 3 months of age between 2011 and 2021. RESULTS: The patients were followed for a median of 3.9 years (Q1-Q3: 2.5-5.75 years). Sapropterin was tapered down and discontinued in 5 patients (6.3%) as their Phe levels remained below 360 µmol/L without treatment. Sapropterin monotherapy was sufficient in 62 patients (77.5%), while 13 (16.2%) required dietary treatment. Phe and tyrosine (Tyr) levels, and Phe:Tyr ratios differed significantly among the patients maintained on sapropterin monotherapy and those started on dietary treatment, but the Phe:Tyr ratio at diagnosis was the most important independent baseline variable (OR: 1.61, 95% CI: 1.15-2.27, p = 0.006), with Phe:Tyr ratio at diagnosis >5.25 associated with dietary treatment (sensitivity: 90.0%, specificity: 81.8%). Genotypic phenotype value (GPV), unavailable at baseline, was also associated with dietary treatment (median GPV 9.2 vs. 3.8, p = 0.006), but some genotypes were not specific to the final treatment modality. DISCUSSION: We propose that the Phe:Tyr ratio at diagnosis is an important indicator to predict dietary requirement in young infants initially managed with sapropterin monotherapy.

COVID-19 in inherited metabolic disorders: Clinical features and risk factors for disease severity.

BACKGROUND: Old age, obesity, and certain chronic conditions are among the risk factors for severe COVID-19. More information is needed on whether inherited metabolic disorders (IMD) confer risk of more severe COVID-19. We aimed to establish COVID-19 severity and associated risk factors in patients with IMD currently followed at a single metabolic center. METHODS: Among all IMD patients followed at a single metabolic referral center who had at least one clinic visit since 2018, those with accessible medical records were reviewed for SARS-CoV-2 tests. COVID-19 severity was classified according to the WHO recommendations, and IMD as per the international classification of IMD. RESULTS: Among the 1841 patients with IMD, 248 (13.5%) had tested positive for COVID-19, 223 of whom gave consent for inclusion in the study (131 children and 92 adults). Phenylalanine hydroxylase (48.4%) and biotinidase (12.1%) deficiencies were the most common diagnoses, followed by mucopolysaccharidoses (7.2%). 38.1% had comorbidities, such as neurologic disabilities (22%) or obesity (9.4%). The majority of COVID-19 episodes were asymptomatic (16.1%) or mild (77.6%), but 6 patients (2.7%) each had moderate and severe COVID-19, and two (0.9%) had critical COVID-19, both of whom died. 3 patients had an acute metabolic decompensation during the infection. Two children developed multisystem inflammatory syndrome (MIS-C). Long COVID symptoms were present in 25.2%. Presence of comorbidities was significantly associated with more severe COVID-19 in adults with IMD (p < 0.01), but not in children (p = 0.45). Compared to other categories of IMD, complex molecule degradation disorders were significantly associated with more severe COVID-19 in children (p < 0.01); such a significant IMD category distinction was not found in adults. DISCUSSION: This is the largest study on COVID-19 in IMD patients relying on real-word data and objective definitions, and not on merely expert opinions or physician surveys. COVID-19 severity and long COVID incidence in IMD are probably similar to the general population, and the risk of acute metabolic decompensation is not likely to be greater than that in other acute infections. Disease category (complex molecule degradation) in children, and comorbidities in adults may be associated with COVID-19 severity in IMD. Additionally, the first documented accounts of COVID-19 in 27 different IMD are recorded. The high occurrence of MIS-C may be coincidental, but warrants further study.

Levodopa-refractory hyperprolactinemia and pituitary findings in inherited disorders of biogenic amine metabolism.

Elevated serum prolactin concentrations occur in inherited disorders of biogenic amine metabolism because dopamine deficiency leads to insufficient inhibition of prolactin secretion. This work from the International Working Group on Neurotransmitter Related Disorders (iNTD) presents the results of the first standardized study on levodopa-refractory hyperprolactinemia (LRHP; >1000 mU/L) and pituitary magnetic resonance imaging (MRI) abnormalities in patients with inherited disorders of biogenic amine metabolism. Twenty-six individuals had LRHP or abnormal pituitary findings on MRI. Tetrahydrobiopterin deficiencies were the most common diagnoses (n = 22). The median age at diagnosis of LRHP was 16 years (range: 2.5-30, 1st-3rd quartiles: 12.25-17 years). Twelve individuals (nine females) had symptoms attributed to hyperprolactinemia: menstruation-related abnormalities (n = 7), pubertal delay or arrest (n = 5), galactorrhea (n = 3), and decreased sexual functions (n = 2). MRI of the pituitary gland was obtained in 21 individuals; six had heterogeneity/hyperplasia of the gland, five had adenoma, and 10 had normal findings. Eleven individuals were treated with the dopamine agonist cabergoline, ameliorating the hyperprolactinemia-related symptoms in all those assessed. Routine monitoring of these symptoms together with prolactin concentrations, especially after the first decade of life, should be taken into consideration during follow-up evaluations. The potential of slow-release levodopa formulations and low-dose dopamine agonists as part of first-line therapy in the prevention and treatment of hyperprolactinemia should be investigated further in animal studies and human trials. This work adds hyperprolactinemia-related findings to the current knowledge of the phenotypic spectrum of inherited disorders of biogenic amine metabolism.

Clinico-radiological features, molecular spectrum, and identification of prognostic factors in developmental and epileptic encephalopathy due to inosine triphosphate pyrophosphatase (ITPase) deficiency.

Developmental and epileptic encephalopathy 35 (DEE 35) is a severe neurological condition caused by biallelic variants in ITPA, encoding inosine triphosphate pyrophosphatase, an essential enzyme in purine metabolism. We delineate the genotypic and phenotypic spectrum of DEE 35, analyzing possible predictors for adverse clinical outcomes. We investigated a cohort of 28 new patients and reviewed previously described cases, providing a comprehensive characterization of 40 subjects. Exome sequencing was performed to identify underlying ITPA pathogenic variants. Brain MRI (magnetic resonance imaging) scans were systematically analyzed to delineate the neuroradiological spectrum. Survival curves according to the Kaplan-Meier method and log-rank test were used to investigate outcome predictors in different subgroups of patients. We identified 18 distinct ITPA pathogenic variants, including 14 novel variants, and two deletions. All subjects showed profound developmental delay, microcephaly, and refractory epilepsy followed by neurodevelopmental regression. Brain MRI revision revealed a recurrent pattern of delayed myelination and restricted diffusion of early myelinating structures. Congenital microcephaly and cardiac involvement were statistically significant novel clinical predictors of adverse outcomes. We refined the molecular, clinical, and neuroradiological characterization of ITPase deficiency, and identified new clinical predictors which may have a potentially important impact on diagnosis, counseling, and follow-up of affected individuals.

Homozygous missense VPS16 variant is associated with a novel disease, resembling mucopolysaccharidosis-plus syndrome in two siblings.

Disorders of intracellular trafficking are a group of inherited disorders, which often display multisystem phenotypes. Vacuolar protein sorting (VPS) subunit C, composed of VPS11, VPS18, VPS16, and VPS33A proteins, is involved in tethering of endosomes, lysosomes, and autophagosomes. Our group and others have previously described patients with a specific homozygous missense VPS33A variant, exhibiting a storage disease phenotype resembling mucopolysaccharidosis (MPS), termed "MPS-plus syndrome." Here, we report two siblings from a consanguineous Turkish-Arabic family, who have overlapping features of MPS and intracellular trafficking disorders, including short stature, coarse facies, developmental delay, peripheral neuropathy, splenomegaly, spondylar dysplasia, congenital neutropenia, and high-normal glycosaminoglycan excretion. Whole exome sequencing and familial segregation analyses led to the homozygous NM_022575.3:c.540G>T; p.Trp180Cys variant in VPS16 in both siblings. Multiple bioinformatic methods supported the pathogenicity of this variant. Different monoallelic null VPS16 variants and a homozygous missense VPS16 variant had been previously associated with dystonia. A biallelic intronic, probably splice-altering variant in VPS16, causing an MPS-plus syndrome-like disease has been very recently reported in two individuals. The siblings presented herein display no dystonia, but have features of a multisystem storage disorder, representing a novel MPS-plus syndrome-like disease, associated for the first time with VPS16 missense variants.

Brain MR patterns in inherited disorders of monoamine neurotransmitters: An analysis of 70 patients.

Inherited monoamine neurotransmitter disorders (iMNDs) are rare disorders with clinical manifestations ranging from mild infantile hypotonia, movement disorders to early infantile severe encephalopathy. Neuroimaging has been reported as non-specific. We systematically analyzed brain MRIs in order to characterize and better understand neuroimaging changes and to re-evaluate the diagnostic role of brain MRI in iMNDs. 81 MRIs of 70 patients (0.1-52.9 years, 39 patients with tetrahydrobiopterin deficiencies, 31 with primary disorders of monoamine metabolism) were retrospectively analyzed and clinical records reviewed. 33/70 patients had MRI changes, most commonly atrophy (n = 24). Eight patients, six with dihydropteridine reductase deficiency (DHPR), had a common pattern of bilateral parieto-occipital and to a lesser extent frontal and/or cerebellar changes in arterial watershed zones. Two patients imaged after acute severe encephalopathy had signs of profound hypoxic-ischemic injury and a combination of deep gray matter and watershed injury (aromatic l-amino acid decarboxylase (AADCD), tyrosine hydroxylase deficiency (THD)). Four patients had myelination delay (AADCD; THD); two had changes characteristic of post-infantile onset neuronal disease (AADCD, monoamine oxidase A deficiency), and nine T2-hyperintensity of central tegmental tracts. iMNDs are associated with MRI patterns consistent with chronic effects of a neuronal disorder and signs of repetitive injury to cerebral and cerebellar watershed areas, in particular in DHPRD. These will be helpful in the (neuroradiological) differential diagnosis of children with unknown disorders and monitoring of iMNDs. We hypothesize that deficiency of catecholamines and/or tetrahydrobiopterin increase the incidence of and the CNS susceptibility to vascular dysfunction.