Using exome sequencing, we identify SERAC1 mutations as the cause of MEGDEL syndrome, a recessive disorder of dystonia and deafness with Leigh-like syndrome, impaired oxidative phosphorylation and 3-methylglutaconic aciduria. We localized SERAC1 at the interface between the mitochondria and the endoplasmic reticulum in the mitochondria-associated membrane fraction that is essential for phospholipid exchange. A phospholipid analysis in patient fibroblasts showed elevated concentrations of phosphatidylglycerol-34:1 (where the species nomenclature denotes the number of carbon atoms in the two acyl chains:number of double bonds in the two acyl groups) and decreased concentrations of phosphatidylglycerol-36:1 species, resulting in an altered cardiolipin subspecies composition. We also detected low concentrations of bis(monoacyl-glycerol)-phosphate, leading to the accumulation of free cholesterol, as shown by abnormal filipin staining. Complementation of patient fibroblasts with wild-type human SERAC1 by lentiviral infection led to a decrease and partial normalization of the mean ratio of phosphatidylglycerol-34:1 to phosphatidylglycerol-36:1. Our data identify SERAC1 as a key player in the phosphatidylglycerol remodeling that is essential for both mitochondrial function and intracellular cholesterol trafficking.

BackgroundMorquio A syndrome (or mucopolysaccharidosis IVa) is an ultra-rare multi-organ disease, resulting in significantly impaired functional capacity, mobility and quality of life (QoL).MethodsThis patient-reported outcomes survey evaluated the global burden of Morquio A among adults (≥18 years, N = 27) and children (7-17 years, N = 36), including the impact on mobility, QoL, pain and fatigue. QoL was assessed using the general Health-Related Quality of Life (HRQoL) questionnaire (the EuroQol [EQ]-5D-5L). Pain and pain interference with daily activities were assessed using the Brief Pain Inventory Short Form (BPI-SF) in adults and the Adolescent Pediatric Pain Tool (APPT) in children. Fatigue was assessed by questioning the patients on the number of evenings in a week they felt extremely tired.ResultsThe clinical data showed a wide heterogeneity in clinical manifestations between patients, with the majority of patients showing differing levels of endurance, short stature, bone and joint abnormalities, abnormal gait and eye problems. Mobility was considerably impaired: 44.4% of children and 85.2% of adult patients were using a wheelchair. High wheelchair reliance significantly reduced QoL. This was mainly driven by reduced scores in the Mobility, Self-care, and Usual Activity domains. The HRQoL utility values were 0.846, 0.582 and 0.057 respectively in adults not using a wheelchair, using a wheelchair only when needed and always using a wheelchair; values were 0.534, 0.664 and –0.180 respectively in children. Employed adult patients had a better HRQoL than unemployed patients (HRQoL utility value 0.640 vs. 0.275, respectively).64% of children and 74% of adult patients had joint pain; fatigue was reported by 69% of children and 63% of adults. Overall, increased mobility was associated with more severe and widespread pain and more fatigue.ConclusionsThe HRQoL of Morquio A patients is mainly driven by the ability to remain independently mobile without becoming wheelchair dependent. Their QoL reduces dramatically if they always have to use their wheelchair. Even a slightly better mobility (wheelchair use only when needed) greatly improves QoL. Maintenance of functional capacity and mobility paired with better pain management are likely to improve QoL.

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Objective3‐Methylglutaconic aciduria, dystonia–deafness, hepatopathy, encephalopathy, Leigh‐like syndrome (MEGDHEL) syndrome is caused by biallelic variants in SERAC1.MethodsThis multicenter study addressed the course of disease for each organ system. Metabolic, neuroradiological, and genetic findings are reported.ResultsSixty‐seven individuals (39 previously unreported) from 59 families were included (age range = 5 days–33.4 years, median age = 9 years). A total of 41 different SERAC1 variants were identified, including 20 that have not been reported before. With the exception of 2 families with a milder phenotype, all affected individuals showed a strikingly homogeneous phenotype and time course. Severe, reversible neonatal liver dysfunction and hypoglycemia were seen in >40% of all cases. Starting at a median age of 6 months, muscular hypotonia (91%) was seen, followed by progressive spasticity (82%, median onset = 15 months) and dystonia (82%, 18 months). The majority of affected individuals never learned to walk (68%). Seventy‐nine percent suffered hearing loss, 58% never learned to speak, and nearly all had significant intellectual disability (88%). Magnetic resonance imaging features were accordingly homogenous, with bilateral basal ganglia involvement (98%); the characteristic “putaminal eye” was seen in 53%. The urinary marker 3‐methylglutaconic aciduria was present in virtually all patients (98%). Supportive treatment focused on spasticity and drooling, and was effective in the individuals treated; hearing aids or cochlear implants did not improve communication skills.InterpretationMEGDHEL syndrome is a progressive deafness–dystonia syndrome with frequent and reversible neonatal liver involvement and a strikingly homogenous course of disease. Ann Neurol 2017;82:1004–1015

Proteoglycan (PG) synthesis begins with the sequential addition of a "linker chain", made up of four sugar residues, to a specific region of a core protein. Defects in the enzymes catalyzing steps two to four of the linker chain synthesis have been shown to cause autosomal recessive human phenotypes while no mutation has yet been reported in humans for the xylosyltransferases 1 and 2 (XT1 and XT2), the initiating enzymes in the linker chain formation. Here, we present a consanguineous Turkish family with two affected individuals presenting with short stature, distinct facial features, alterations of fat distribution, and moderate intellectual disability. X-rays showed only mild skeletal changes in the form of a short femoral neck, stocky and plump long bones and thickened ribs. Using a combination of whole-exome sequencing (WES), determination of homozygous stretches by WES variants, and classical linkage analysis, we identified the homozygous missense mutation c.C1441T in XYLT1, encoding XT1, within a large homozygous stretch on chromosome 16p13.12-p12.1. The mutation co-segregated with the phenotype in the family, is not found in over 13,000 alleles in the exome variant server and is predicted to change a highly conserved arginine at position 481 (p.R481W) located in the putative catalytical domain. Immunostaining of primary patient fibroblasts showed a loss of predominance of Golgi localization in mutant cells. Moreover, western blot analysis of decorin in cell culture supernatant demonstrated glycosylation differences between patient and control cells. Our data provide evidence that functional alterations of XT1 cause an autosomal recessive short stature syndrome associated with intellectual disability.

The aim of the present study is to clarify the low density lipoprotein apheresis procedure for pediatric patients with homozygous familial hypercholesterolemia (FH) in terms of efficacy, adverse effects and difficulties. The follow-up was carried out using an open, prospective uncontrolled clinical design. Data were collected from 10 patients (with an average age of 8.4 +/- 4.7 years) with FH treated with double filtration plasmapheresis. The total time span of follow-up covered five years (30.2 +/- 17.8 months [range 9-60 months]) and more than 600 sessions (62.1 +/- 35.5 sessions per patient [range 18-120 sessions]) were evaluated. The mean low density lipoprotein cholesterol (LDL-C) pre-treatment value was 375.5 +/- 127.5 mg/dL, and the post-treatment value was 147.5 +/- 73.9 mg/dL. This corresponded to a 62.8 +/- 10.3% (43-73%) acute reduction of LDL-C, while the mean high density lipoprotein cholesterol losses amounted to 41%. The chronic reduction in LDL-C ranged from 18 to 52%, with a mean level of 36.4 +/- 11.7%. The most frequently occurring technical problems were related to blood lines: puncture difficulties (4.5%), insufficient blood flow (3.5%), and obturation of the blood lines (2.4%). The main clinical adverse effects were hypotension (0.2%), chills/feeling cold (0.1%), and nausea and vomiting (0.2%). We observed that the low pediatric patient tolerance is the main problem in compliance with treatment. In conclusion, LDL apheresis, started under the age of eight years, combined with lipid-lowering drugs, provides a safe and effective lowering of the mean LDL-C levels in pediatric homozygous FH; and there are more problems with compliance for pediatric LDL apheresis than in the adult population.

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Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder which primarily affects the gastrointestinal and nervous systems. This disease is caused by mutations in the nuclear TYMP gene, which encodes for thymidine phosphorylase, an enzyme required for the normal metabolism of deoxynucleosides, thymidine, and deoxyuridine. The subsequent elevated systemic concentrations of deoxynucleosides lead to increased intracellular concentrations of their corresponding triphosphates, and ultimately mitochondrial failure due to progressive accumulation of mitochondrial DNA (mtDNA) defects and mtDNA depletion. Currently, there are no treatments for MNGIE where effectiveness has been evidenced in clinical trials. This Phase 2, multi-centre, multiple dose, open label trial without a control will investigate the application of erythrocyte-encapsulated thymidine phosphorylase (EE-TP) as an enzyme replacement therapy for MNGIE. Three EE-TP dose levels are planned with patients receiving the dose level that achieves metabolic correction. The study duration is 31 months, comprising 28 days of screening, 90 days of run-in, 24 months of treatment and 90 days of post-dose follow-up. The primary objectives are to determine the safety, tolerability, pharmacodynamics, and efficacy of multiple doses of EE-TP. The secondary objectives are to assess EE-TP immunogenicity after multiple dose administrations and changes in clinical assessments, and the pharmacodynamics effect of EE-TP on clinical assessments.