PURPOSE:Ketone bodies represent an important energy source and can contribute much to the energy supply of the brain. Mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase deficiency (HMGCS2D) is an autosomal recessive disorder of ketogenesis caused by biallelic variants in HMGCS2. Only 59 patients with this disorder have been reported so far. METHODS:We performed a comprehensive literature search to identify all published cases of HMGCS2D (n = 59). Additionally, the data of 16 patients with this disorder who are yet undescribed were collected. Clinical course, biochemical findings, and mutation data are highlighted and discussed. An overview on all HMGCS2 variants reported in patients is provided. RESULTS:Sixty-eight patients (91%) presented with an acute metabolic decompensation, mostly within the first year of life but beyond the neonatal period. Asymptomatic individuals were identified in several families. Six patients (8%) had died, mainly during the initial metabolic crisis. The neurologic long-term outcome of surviving patients was favorable with almost all patients (98%) showing normal development. Only 1 variant was identified to be common, (HMGCS2) NM_005518.4:c.634G>A p.(Gly212Arg), and found in 6 families. No genotype-phenotype correlation can be established. CONCLUSION:This comprehensive data analysis provides an overview on all published patients reported with HMGCS2D, including a list of HMGCS2 variants identified in affected individuals.

Empagliflozin has been successfully repurposed for treating neutropenia and neutrophil dysfunction in patients with glycogen storage disease type 1b (GSD 1b), however, data in infants are missing. We report on efficacy and safety of empagliflozin in infants with GSD 1b. This is an international retrospective case series on 21 GSD 1b infants treated with empagliflozin (total treatment time 20.6 years). Before starting empagliflozin (at a median age of 8.1 months with a median dose of 0.3 mg/kg/day) 12 patients had clinical signs and symptoms of neutrophil dysfunction. Six of these previously symptomatic patients had no further neutropenia/neutrophil dysfunction-associated findings on empagliflozin. Eight patients had no signs and symptoms of neutropenia/neutrophil dysfunction before start and during empagliflozin treatment. One previously asymptomatic individual with a horseshoe kidney developed a central line infection with pyelonephritis and urosepsis during empagliflozin treatment. Of the 10 patients who were treated with G-CSF before starting empagliflozin, this was stopped in four and decreased in another four. Eleven individuals were never treated with G-CSF. While in 17 patients glucose homeostasis remained stable on empagliflozin, four showed glucose homeostasis instability in the introductory phase. In 17 patients, no other side effects were reported, while genital ( n = 2) or oral ( n = 1) candidiasis and skin infection (n = 1) were reported in the remaining four. Empagliflozin had a good effect on neutropenia/neutrophil dysfunction -related signs and symptoms and a favourable safety profile in infants with GSD 1b and therefore qualifies for further exploration as first line treatment.

Newborn screening (NBS) for isovaleric acidemia (IVA) reduces mortality and morbidity; however, it has also resulted in the detection of individuals with an asymptomatic or mild presentation for which early detection via newborn screening has not been proven to alter neurological outcome. We reevaluated biochemical and molecular data for newborns flagged positive for IVA in aim of developing a new screening algorithm to exclude the latter from positive screening. Among 2 794 365 newborns underwent routine newborn screening in Israel, 412 flagged positive for IVA, of which, 371 were false positives on recall sample testing and 41 positive newborns were referred to the clinic. 38/41 have biochemical and molecular confirmation in keeping with IVA. Among the 38 patients, 32% (12/38) were classified as symptomatic while, 68% (26/38) were classified as asymptomatic. 69% of the latter group harbor the known variant associated with mild potentially asymptomatic phenotype, c.932C>T; p. Ala311Val. Among asymptomatic patients, only 46% (12/26) are currently treated. Two novel variants have been detected in the IVD gene: c.487G>A; p. Ala163Thr and c.985A>G; p. Met329Val. Cut-off recalculation, of referred newborns' initial biochemical results, after classifying the referred patients to two binary groups of symptomatic and asymptomatic, resulted in an improved NBS algorithm comprising of C5 >5 μM and C5/C2>0.2 and C5/C3>4 flagging only those likely to have the classic symptomatic phenotype.

Galactosemia is an inborn disorder of carbohydrate metabolism of which early detection can prevent severe illness. Although the assay for galactose-1-phosphate uridyltransferase (GALT) enzyme activity has been available since the 1960s, many issues prevented it from becoming universal. In order to develop the Israeli newborn screening pilot algorithm for galactosemia, flow injection analysis tandem mass spectrometry measurement of galactose-1-phosphate in archived dried blood spots from newborns with classical galactosemia, galactosemia variants, epimerase deficiency, and normal controls, was conducted. Out of 431 330 newborns screened during the pilot study (30 months), two with classical galactosemia and four with epimerase deficiency were identified and confirmed. Five false positives and no false negatives were recorded. Following this pilot study, the Israeli final and routine newborn screening algorithm, as recommended by the Advisory Committee to the National Newborn Screening Program, now consists of galactose-1-phosphate measurement integrated into the routine tandem mass spectrometry panel as the first-tier screening test, and GALT enzyme activity as the second-tier performed to identify only newborns suspected to be at risk for classical galactosemia. The GALT enzyme activity cut-off used in the final algorithm was lowered in order to avoid false positives.

Introduction: Hereditary orotic aciduria is an extremely rare, autosomal recessive disease caused by deficiency of uridine monophosphate synthase. Untreated, affected individuals may develop refractory megaloblastic anemia, neurodevelopmental disabilities, and crystalluria. Newborn screening has the potential to identify and enable treatment of affected individuals before they become significantly ill.Methods: Measuring orotic acid as part of expanded newborn screening using flow injection analysis tandem mass spectrometry.Results: Since the addition of orotic acid measurement to the Israeli routine newborn screening program, 1,492,439 neonates have been screened. The screen has identified ten Muslim Arab newborns that remain asymptomatic so far, with DBS orotic acid elevated up to 10 times the upper reference limit. Urine organic acid testing confirmed the presence of orotic aciduria along with homozygous variations in the UMPS gene.Conclusion: Newborn screening measuring of orotic acid, now integrated into the routine tandem mass spectrometry panel, is capable of identifying neonates with hereditary orotic aciduria.

The high-affinity copper transporter CTR1 is encoded by CTR1 (SLC31A1), a gene locus for which no detailed genotype-phenotype correlations have previously been reported. We describe identical twin male infants homozygous for a novel missense variant NM_001859.4:c.284 G > A (p.Arg95His) in CTR1 with a distinctive autosomal recessive syndrome of infantile seizures and neurodegeneration, consistent with profound central nervous system copper deficiency. We used clinical, biochemical and molecular methods to delineate the first recognized examples of human CTR1 deficiency. These included clinical phenotyping, brain imaging, assays for copper, cytochrome c oxidase (CCO), and mitochondrial respiration, western blotting, cell transfection experiments, confocal and electron microscopy, protein structure modeling and fetal brain and cerebral organoid CTR1 transcriptome analyses. Comparison with two other critical mediators of cellular copper homeostasis, ATP7A and ATP7B, genes associated with Menkes disease and Wilson disease, respectively, revealed that expression of CTR1 was highest. Transcriptome analyses identified excitatory neurons and radial glia as brain cell types particularly enriched for copper transporter transcripts. We also assessed the effects of Copper Histidinate in the patients' cultured cells and in the patients, under a formal clinical protocol. Treatment normalized CCO activity and enhanced mitochondrial respiration in vitro, and was associated with modest clinical improvements. In combination with present and prior studies, these infants' clinical, biochemical and molecular phenotypes establish the impact of this novel variant on copper metabolism and cellular homeostasis and illuminate a crucial role for CTR1 in human brain development. CTR1 deficiency represents a newly defined inherited disorder of brain copper metabolism.

Urea cycle disorders (UCDs), including OTC deficiency (OTCD), are life-threatening diseases with a broad clinical spectrum. Early diagnosis and initiation of treatment based on a newborn screening (NBS) test for OTCD with high specificity and sensitivity may contribute to reduction of the significant complications and high mortality. The efficacy of incorporating orotic acid determination into routine NBS was evaluated. Combined measurement of orotic acid and citrulline in archived dried blood spots from newborns with urea cycle disorders and normal controls was used to develop an algorithm for routine NBS for OTCD in Israel. Clinical information and genetic confirmation results were obtained from the follow-up care providers. About 1147986 newborns underwent routine NBS including orotic acid determination, 25 of whom were ultimately diagnosed with a UCD. Of 11 newborns with OTCD, orotate was elevated in seven but normal in two males with early-onset and two males with late-onset disease. Orotate was also elevated in archived dried blood spots of all seven retrospectively tested historical OTCD patients, only three of whom had originally been identified by NBS with low citrulline and elevated glutamine. Among the other UCDs emerge, three CPS1D cases and additional three retrospective CPS1D cases otherwise reported as a very rare condition. Combined levels of orotic acid and citrulline in routine NBS can enhance the detection of UCD, especially increasing the screening sensitivity for OTCD and differentiate it from CPS1D. Our data and the negligible extra cost for orotic acid determination might contribute to the discussion on screening for proximal UCDs in routine NBS.

BACKGROUND:Maple syrup urine disease is a rare autosomal-recessive aminoacidopathy, caused by deficient branched-chain 2-keto acid dehydrogenase (BCKD), with subsequent accumulation of branched-chain amino acids (BCAAs): leucine, isoleucine and valine. While most cases of MSUD are classic, some 20% of cases are non-classic variants, designated as intermediate- or intermittent-types. Patients with the latter form usually develop normally and are cognitively intact, with normal BCAA levels when asymptomatic. However, intercurrent febrile illness and catabolism may cause metabolic derailment with life-threatening neurological sequelae. Thus, early detection and dietary intervention are warranted in intermittent MSUD.PATIENTS AND METHODS:We describe eight patients from four unrelated families, diagnosed with intermittent MSUD. Their presenting symptoms during metabolic crises varied from confusion and decreased consciousness, to ataxia, and acute psychosis. Molecular confirmation of MSUD was pursued via sequencing of the BCKDHA, BCKDHB and DBT genes.RESULTS:All affected individuals were found to harbor bi-allelic pathogenic variants in either BCKDHB or DBT. Of the seven variants, four variants in BCKDHB (p.G101D, p. V103A, p. A221D, p. Y195C) and one variant in DBT (p.K427E) were not previously described.CONCLUSIONS:While newborn screening programs allow for early detection of classic MSUD, cases of the intermittent form might go undetected, and present later in childhood following metabolic derailment, with an array of non-specific symptoms. Our experience with the families reported herein adds to the current knowledge regarding the phenotype and mutational spectrum of this unique inborn error of branched-chain amino acid metabolism, and underscore the high index of suspicion required for its diagnosis.

A previously healthy 4-year-old boy presented with drowsiness and Kussmaul respiration following 2 days of abdominal pain, anorexia, and repeated vomiting. Venous blood pH was 7.07 (reference interval, 7.33–7.44); pCO2, 24 mm Hg (reference interval, 37–53); bicarbonate, 7.0 mmol/L (reference interval, 24–28); base excess, −21.6 mmol/L; and calculated anion gap, 23 mmol/L (reference interval, 3–11). Plasma glucose was 86 mg/dL (reference interval, 70–99) and lactate was 2.2 mmol/L (reference interval, 0.5–2.2). Urine dipstick testing was negative for glucose and strongly positive for ketones. Results of urine organic acid analysis by GC-MS are shown in Fig. 1. Fig. 1. Analysis of organic acids in the patient's urine by GC-MS. Abnormal metabolites are labeled in bold text. Urine organic acids were extracted into ethyl acetate/ether, converted to trimethylsilyl derivatives, and analyzed on an Agilent GC 7890A/MS 5975 system equipped with an Agilent HP-5MS (30 m, 0.25 mm × 0.25 μm) column. Internal standards (IS): 2-phenylbutyric, tropic, and margaric acids. The high anion gap implied accumulation of an abnormal acid rather than renal or gastrointestinal loss of bicarbonate as the cause of this …

A 2-month-old girl presents with jaundice, pallor, and abdominal distention. She was born by normal delivery at term weighing 2,380 g. Her 22-month-old brother has tyrosinemia type I detected on newborn screening (NBS) and subsequently confirmed by the presence of succinylacetone on a urine organic acid analysis and demonstration of homozygosity for the IVS8-1(g-c) mutation in the FAH gene. He is doing well and has normal liver function on standard treatment with NTBC (nitisinone) and a tyrosine- and phenylalanine-restricted diet. The parents are first cousins of Christian Arab origin from the north of Israel and confirmed to be heterozygous for the FAH mutation. Prenatal genetic diagnosis performed in the latest pregnancy on chorionic villus sampling indicated that the girl is a heterozygous carrier for the FAH mutation. Findings from her NBS were completely normal, including a negative test for succinylacetone. She is being bottle-fed with a regular infant formula.On examination she looks pale and sweaty, although alert. Her abdomen is swollen but not tender, with a firm liver edge palpable below the costal margin, spleen not palpable. Initial laboratory results (Table) reveal a blood sugar level of 34 mg/dL (1.9 mmol/L), elevated hepatocellular and cholestatic liver enzyme levels, direct hyperbilirubinemia, hypoalbuminemia, and abnormal coagulation studies consistent with synthetic liver failure. She is treated with a glucose infusion and intramuscular vitamin K. In light of the family history and her presentation with synthetic liver failure, tyrosinemia type I is highly suspected despite the negative prenatal genetic testing and NBS. Urine organic acid analysis, indeed, reveals increased excretion of tyrosine metabolites, but succinylacetone is not detected. The results of her plasma amino acid profile (Table) suggest a different diagnosis.Inborn errors of metabolism (IEMs) are an important cause of liver failure in neonates and young infants. (1) Many IEMs are treatable, including disorders of carbohydrate metabolism, such as galactosemia and hereditary fructose intolerance; disorders of amino acid metabolism and transport, such as tyrosinemia type I; the urea cycle disorders, including citrin deficiency; and fatty acid oxidation disorders. Other IEMs to consider include mitochondrial respiratory chain disorders, congenital disorders of glycosylation, transaldolase deficiency, and Niemann-Pick type C disease. In this patient, tyrosinemia type I was suspected because of the history of an affected sibling but was unlikely in view of the negative testing for succinylacetone. Nevertheless, rare cases of tyrosinemia type I with undetectable succinylacetone have been reported. (2) Particularly in the context of parental consanguinity, the possibility of a second IEM in the same family also needs to be considered.Plasma amino acid analysis revealed elevated citrulline, arginine, threonine, lysine, and methionine levels; low glutamine levels; and an elevated threonine-to-serine ratio (Table). α1-Fetoprotein level was markedly elevated. These findings were highly suggestive of citrullinemia type II, also known as citrin deficiency. Sequencing of the citrin-encoding gene SLC25A13 revealed a novel homozygous c.848G>T p.G283V mutation predicted to be pathogenic.Citrin, an aspartate-glutamate mitochondrial inner membrane transporter, is defective in citrullinemia type II. Citrin is essential for normal functioning of the urea cycle by providing aspartate for the synthesis of argininosuccinic acid (Fig). Citrin is also an important component of the malate-aspartate transporter, which transports cytosolic NADH from glycolysis into the mitochondria. Carbohydrate ingestion causes an increase in the cytosolic NADH/NAD+ ratio, which inhibits aerobic glycolysis in cells, leading to energy shortage in hepatocytes and suppression of ureogenesis. Furthermore, increased NADH also impairs galactose metabolism, leading to accumulation of other toxic compounds in hepatocytes, similar to galactosemia.The clinical phenotype of citrin deficiency varies according to the age at onset. (3) The neonatal/infantile form presents with transient intrahepatic cholestatic hepatitis, whereas the late adolescence or adult form presents with neuropsychiatric symptoms associated with hyperammonemia. In the intervening period, affected children may be apparently asymptomatic but have failure to thrive, dyslipidemia, fatty liver, and aversion to carbohydrates. (4)Infants may present with prolonged cholestatic jaundice and failure to thrive, accompanied by hypoalbuminemia, abnormal coagulation profile, liver dysfunction, hypoglycemia, hemolytic anemia, and hypergalactosemia. The plasma amino acid profile shows elevation of not only citrulline but also arginine, methionine, tyrosine, and threonine levels, with an elevated threonine-to-serine ratio. Citrin deficiency might be detected on NBS by elevation of any of the previously mentioned amino acids or as a false-positive for galactosemia screening. However, only approximately 40% of infants with citrin deficiency have an abnormal NBS result. (5) In Israel the proportion is likely to be even lower because galactosemia is not included in the national NBS program. Diagnosis is confirmed by mutation analysis of the SLC25A13 gene.Treatment with a lactose-free formula, as in galactosemia, and provision of medium-chain triglycerides (MCTs) as an alternative source of energy to the hepatocytes should be initiated as soon as the diagnosis of citrin deficiency is suspected in cholestatic infants. (6) After the first year of life, a low-carbohydrate, high-protein, and high-fat diet, as preferred by the patients, is recommended. Administration of arginine, sodium pyruvate, and/or MCTs may be beneficial. Liver transplant may be required to prevent the hyperammonemic episodes and correct the metabolic disturbances. (7)Once citrin deficiency was suspected, glucose infusion was ceased and she was started on a lactose-free formula enriched with additional MCTs. Repeated blood tests showed improvement in hepatocellular and cholestatic liver enzyme levels and blood albumin levels, resolution of her direct hyperbilirubinemia, and normalization of her coagulation studies (Table). She maintained normoglycemia when fed every 3 hours. She was discharged from the hospital after 5 days in good general condition. She is now 7 months of age and continues regular follow-up in the Metabolic Clinic. She has mild global developmental delay and hypotonia. Her weight and height are between the 5th and 10th percentiles for age.

A 50-year-old man with long-standing Crohn disease underwent metabolic investigation as part of evaluation for subacute cognitive decline and confusional state. An infected ulcer present on his left foot for several months was suspected to be pyoderma gangrenosum. Routine biochemistry results including plasma lactate and ammonia were within reference limits. Plasma amino acid examination (high-performance liquid chromatography) on 2 occasions revealed increased arginine at 309 and 377 (reference interval, 15–160) μmol/L and ornithine at 210 and 361 (30–150) μmol/L, while all other amino acids including citrulline and glutamine were within reference limits. Urine organic acid examination (Fig. 1) revealed massively increased excretion of 3-hydroxyisovaleric acid (3-OH-IVA)5 with an otherwise normal profile. Fig. 1. Urine organic acid chromatogram (by GC-MS). Urine organic acids were extracted into ethyl acetate/ether, converted to trimethylsilyl derivatives, and analyzed on an Agilent GC 7890A/MS 5975 system equipped with an Agilent HP-5MS (30 m, 0.25 mm × 0.25 μm) column. Internal standards: 2-phenylbutyric, tropic acid, and margaric acid. Increased arginine is a feature of the urea cycle disorder arginase deficiency, but ornithine, the …

Transaldolase (TALDO) deficiency has various clinical manifestations including liver dysfunction, hepatosplenomegaly, anemia, thrombocytopenia, and dysmorphic features. We report a case presenting prenatally with hyperechogenic bowel and intrauterine growth restriction. The infant was born small for gestational age, with cutis laxa and hypertrichosis. Postnatally, meconium plug was identified, complicated with intestinal obstruction necessitating laparotomy, partial resection of the intestine, and ileostomy. Liver biopsy revealed cholangiolar proliferation and portal fibrosis. He also suffered from persistent congenital thrombocytopenia requiring platelet transfusions and severe hypothyroidism with normal anatomical and structural gland responding only to the combination of T3 and T4 treatment. Neurologically, severe hypotonia and anisocoria were noted at the age of 2 months. Brain MRI was normal. Shortly after the abdominal surgery, a rapid liver failure ensued, which eventually led to his death. Specific metabolic tests ruled out glycosylation disorders, yet urine analysis using 1H NMR showed accumulation of sedoheptulose which was previously described in patients with transaldolase deficiency. Sequencing of the gene-encoding transaldolase (TALDO1) revealed a homozygous stop mutation c.669C>G; p.Tyr223*. In conclusion, we present an infant with a novel homozygous mutation in TALDO1, causing TALDO deficiency, and extend the clinical characteristics of this rare syndrome.

This paper summarizes the results of a group effort to bring together the worldwide available data on patients who are either homozygotes or compound heterozygotes for mutations in MAT1A. MAT1A encodes the subunit that forms two methionine adenosyltransferase isoenzymes, tetrameric MAT I and dimeric MAT III, that catalyze the conversion of methionine and ATP to S-adenosylmethionine (AdoMet). Subnormal MAT I/III activity leads to hypermethioninemia. Individuals, with hypermethioninemia due to one of the MAT1A mutations that in heterozygotes cause relatively mild and clinically benign hypermethioninemia are currently often being flagged in screening programs measuring methionine elevation to identify newborns with defective cystathionine β-synthase activity. Homozygotes or compound heterozygotes for MAT1A mutations are less frequent. Some but not all, such individuals have manifested demyelination or other CNS abnormalities.

IMPORTANCE Hereditary spastic paraplegia is a highly heterogeneous group of neurogenetic disorders with pure and complicated clinical phenotypes. No treatment is available for these disorders. We identified 2 unrelated families, each with 2 siblings with severe methylenetetrahydrofolate reductase (MTHFR) deficiency manifesting a complicated form of adult-onset hereditary spastic paraparesis partially responsive to betaine therapy.OBSERVATIONS Both pairs of siblings presented with a similar combination of progressive spastic paraparesis and polyneuropathy, variably associated with behavioral changes, cognitive impairment, psychosis, seizures, and leukoencephalopathy, beginning between the ages of 29 and 50 years. By the time of diagnosis a decade later, 3 patients were ambulatory and 1 was bedridden. Investigations have revealed severe hyperhomocysteinemia and hypomethioninemia, reduced fibroblast MTHFR enzymatic activity (18%-52% of control participants), and 3 novel pathogenic MTHFR mutations, 2 as compound heterozygotes in one family and 1 as a homozygous mutation in the other family. Treatment with betaine produced a rapid decline of homocysteine by 50% to 70% in all 4 patients and. over 9 to 15 years, improved the conditions of the 3 ambulatory patients.CONCLUSIONS AND RELEVANCE Although severe MTHFR deficiency is a rare cause of complicated spastic paraparesis in adults, it should be considered in select patients because of the potential therapeutic benefit of betaine supplementation.

Background Agenesis of corpus callosum has been associated with several defects of the mitochondrial respiratory chain and the citric acid cycle. We now report the results of the biochemical and molecular studies of a patient with severe neurodevelopmental disease manifesting by agenesis of corpus callosum and optic nerve hypoplasia.Methods and results A mitochondrial disease was suspected in this patient based on the prominent excretion of 2-hydroxyglutaric acid and Krebs cycle intermediates in urine and the finding of increased reactive oxygen species content and decreased mitochondrial membrane potential in her fibroblasts. Whole exome sequencing disclosed compound heterozygosity for two pathogenic variants in the SLC25A1 gene, encoding the mitochondrial citrate transporter. These variants, G130D and R282H, segregated in the family and were extremely rare in controls. The mutated residues were highly conserved throughout evolution and in silico modeling investigations indicated that the mutations would have a deleterious effect on protein function, affecting either substrate binding to the transporter or its translocation mechanism. These predictions were validated by the observation that a yeast strain harbouring the mutations at equivalent positions in the orthologous protein exhibited a growth defect under stress conditions and by the loss of activity of citrate transport by the mutated proteins reconstituted into liposomes.Conclusions We report for the first time a patient with a mitochondrial citrate carrier deficiency. Our data support a role for citric acid cycle defects in agenesis of corpus callosum as already reported in patients with aconitase or fumarate hydratase deficiency.

BACKGROUND:The TMEM70 gene defect was recently identified as a novel cause of autosomal recessive ATP synthase deficiency. Most of the 28 patients with TMEM70 disorder reported to date display a distinctive phenotype characterised by neonatal onset of severe muscular hypotonia hypertrophic cardiomyopathy, facial dysmorphism, profound lactic acidosis, and 3-methylglutaconic aciduria. Almost all share a common Roma descent and are homozygous for a single founder splice site mutation.METHODS:Six new patients from four separate families, with clinical and biochemical diagnosis of ATP synthase deficiency, were studied. TMEM70 sequence analysis of the three exons and their flanking splice junction consensus sequences was performed in all patients. In addition their clinical phenotype and disease course was strictly studied.RESULTS:Four novel deleterious homozygous TMEM70 mutations were identified. The previously described clinical spectrum was expanded to include infantile onset cataract, early onset gastrointestinal dysfunction and congenital hypertonia with multiple contractures resembling arthrogryposis. The first characterisation of fetal presentation of the syndrome is also provided, featuring significant intrauterine growth retardation, severe oligohydramnios, fetal hypotonia, and myocardial wall thickening.CONCLUSIONS:The current report corroborates the previously described unique phenotype of TMEM70 deficiency. The study identifies TMEM70 gene defect as a pan-ethnic disorder and further redefines it as the most common cause of nuclear-origin ATP synthase deficiency.

Creatine and creatine phosphate provide storage and transmission of phosphate-bound energy in muscle and brain. Of the three inborn errors of creatine metabolism causing brain creatine depletion, l-arginine:glycine amidinotransferase (AGAT) deficiency has been described in only two families. We describe clinical and biochemical features, magnetic resonance spectroscopy (MRS) findings and response to creatine supplementation in two siblings with a novel mutation in the AGAT-encoding GATM gene. The sister and brother were evaluated at age 12 and 18years, respectively, because of mild mental retardation, muscle weakness and low weight. Extensive work-up had previously yielded negative results. Electron microscopy of the muscle revealed tubular aggregates and the activity of respiratory chain complexes was decreased in the muscle. Urine organic acid concentrations normalized to urine creatinine concentration were all increased, suggesting a creatine metabolism disorder. Brain MRS was remarkable for absence of creatine. Urine guanidinoacetate levels by tandem mass spectrometry were low, suggesting AGAT deficiency. GATM sequencing revealed a homozygous single nucleotide insertion 1111_1112insA, producing a frame-shift at Met-371 and premature termination at codon 376. Eleven months after commencing treatment with oral creatine monohydrate 100mg/kg/day, repeat MRI/MRS showed significantly increased brain creatine in the sister and a slight increase in the older brother. The parents' impression of improved strength and stamina was substantiated by increased post-treatment versus pre-treatment scores in the Vineland Adaptive Behavior Scale, straight-arm raising and timed up-and-go tests. Similarly, there was an apparent improvement in cognitive function, with significantly increased IQ-scores in the sister and marginal improvement in the brother.

L-2-Hydroxyglutaric aciduria (L2HGA) is a rare, neurometabolic disorder with an autosomal recessive mode of inheritance. Affected individuals only have neurological manifestations, including psychomotor retardation, cerebellar ataxia, and more variably macrocephaly, or epilepsy. The diagnosis of L2HGA can be made based on magnetic resonance imaging (MRI), biochemical analysis, and mutational analysis of L2HGDH. About 200 patients with elevated concentrations of 2-hydroxyglutarate (2HG) in the urine were referred for chiral determination of 2HG and L2HGDH mutational analysis. All patients with increased L2HG (n = 106; 83 families) were included. Clinical information on 61 patients was obtained via questionnaires. In 82 families the mutations were detected by direct sequence analysis and/or multiplex ligation dependent probe amplification (MLPA), including one case where MLPA was essential to detect the second allele. In another case RT-PCR followed by deep intronic sequencing was needed to detect the mutation. Thirty-five novel mutations as well as 35 reported mutations and 14 nondisease-related variants are reviewed and included in a novel Leiden Open source Variation Database (LOVD) for L2HGDH variants (http://www.LOVD.nl/L2HGDH). Every user can access the database and submit variants/patients. Furthermore, we report on the phenotype, including neurological manifestations and urinary levels of L2HG, and we evaluate the phenotype genotype relationship. Hum Mutat 31:380-390, 2010. (C) 2010 Wiley-Liss, Inc.