Inborn errors of metabolism

OBJECTIVE: The purpose of this study was to determine the frequency of non-immune hydrops fetalis (NIHF) among all pregnancies referred for prenatal care at Sultan Qaboos University Hospital (SQUH) during the study period and to evaluate the underlying etiologies of NIH. STUDY DESIGN: All pregnancies referred to SQUH between February 2014 and December 2015 were identified, and all pregnancies meeting the diagnosis of NIHF were included in this study. All cases of NIHF referred to our center during this period underwent standard systematic diagnostic work-up that included biochemical and molecular studies in addition to the standard investigations for hydrops fetalis...

Classical homocystinuria (HCU) is an inborn error of sulfur amino acid metabolism caused by deficient activity of cystathionine β-synthase (CBS), resulting in an accumulation of homocysteine and a concomitant decrease of cystathionine and cysteine in blood and tissues. In mice, the complete lack of CBS is neonatal lethal. In this study, newborn CBS knockout (KO) mice were treated with recombinant polyethyleneglycolylated human truncated CBS (PEG-CBS). Full survival of the treated KO mice, along with a positive impact on metabolite levels in plasma, liver, brain, and kidneys, was observed...

BACKGROUND: Continuous renal replacement therapies (CRRTs) either as continuous venovenous hemofiltration (CVVH) or hemodiafiltration (CVVHD) are used frequently in critically ill children. Many clinical variables and technical issues are known to affect the result. The factors that could be modified to increase the survival of renal replacement are sought. As a contribution, we present the data on 104 patients who underwent CRRT within a 7-year period. MATERIALS AND METHOD: A total of 104 patients admitted between 2009 and 2016 were included in the study...

Inborn errors of hepatic metabolism are because of deficiencies commonly within a single enzyme as a consequence of heritable mutations in the genome. Individually such diseases are rare, but collectively they are common. Advances in genome-wide association studies and DNA sequencing have helped researchers identify the underlying genetic basis of such diseases. Unfortunately, cellular and animal models that accurately recapitulate these inborn errors of hepatic metabolism in the laboratory have been lacking...

Defects of phospholipids remodelling and synthesis are inborn errors of metabolism responsible for various clinical presentations including spastic paraplegia, retinopathy, optic atrophy, myo- and cardiomyopathies, and osteo-cutaneous manifestations. DDHD1 encodes a phospholipase A1, which is involved in the remodelling of phospholipids. We previously described a relatively pure hereditary spastic paraplegia (HSP) phenotype associated with mutations in DDHD1. Here we report a complex form of HSP associated with retinal dystrophy and a pattern of neurodegeneration with brain iron accumulation (NBIA) on brain MRI, due to a novel homozygous mutation in DDHD1...

Deficiency or diminished activity of a cobalamin dependent enzyme methylmalonyl-CoA mutase causes inborn error of metabolism called methylmalonic acidemia (MMA). In this study we elucidated the spectrum of mutations in 21 Indian mut MMA patients by direct sequencing. Sequence analysis identified a total of 70 mutations in exon 2, 9, 11 and 12 of MUT gene. Out of which 26 mutations were predicted to be deleterious and rest were benign. The 23 novel mutations consist of four nonsense mutations (p.N6*, p.G539*, p...

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive congenital malformation syndrome caused by mutations in the 7-dehydrocholesterol reductase gene. This inborn error of cholesterol synthesis leads to elevated concentrations of 7-dehydrocholesterol (7-DHC). 7-DHC also serves as the precursor for vitamin D synthesis. Limited data is available on vitamin D levels in individuals with SLOS. Due to elevated concentrations of 7-DHC, we hypothesized that vitamin D status would be abnormal and possibly reach toxic levels in patients with SLOS...

Artificial sweeteners are used in protein substitutes intended for the dietary management of inborn errors of metabolism (Phenylketonuria, PKU) to improve the variety of medical foods available to patients and ensure dietary adherence to the prescribed course of dietary management. These patients can be exposed to artificial sweeteners from the combination of free and prescribed foods. Young children have a higher risk of exceeding acceptable daily intakes (ADI) for additives than adults due to higher food intakes per kg body weight...

Asparagine synthetase deficiency is a rare inborn error of metabolism caused by a defect in ASNS, a gene encoding asparagine synthetase. It manifests with a severe neurological phenotype manifesting as severe developmental delay, congenital microcephaly, spasticity and refractory seizures. To date, nineteen patients from twelve unrelated families have been identified. Majority of the mutations are missense and nonsense mutations in homozygous or compound heterozygous state. We add another case from India which harbored a novel homozygous missense variation in exon 11 and compare the current case with previously reported cases...

BACKGROUND: Tandem mass spectrometry (TMS)-based newborn screening has been proven successful as one of the public healthcare programs, although the practicability has not yet been specifically addressed. METHODS: Sixty residual dried blood spot (DBS) specimens from confirmation/diagnosis-insufficient cases discovered by TMS screening were analyzed by targeted next generation sequencing (TNGS) assay. RESULTS: In total, 26, 11, 9, and 14 cases were diagnosed as positive, high risk, low risk, and negative, respectively...

OBJECTIVE: Hypophosphatasia (HPP) is an inborn error of metabolism with significant morbidity and mortality. Its presentation is non-specific leading to delay or missed diagnosis. Low ALP is a diagnostic test. Unlike high ALP, low level is commonly un-flagged by laboratories as abnormal. A new treatment has proved to be effective in HPP. We aim to study frequency of flagging of low ALP level by laboratory and the clinical manifestations of patients presenting with low ALP for a possible diagnosis of HPP...

BACKGROUND: Newborn screening (NBS) is an established screening procedure in many countries worldwide, aiming at the early detection of inborn errors of metabolism. For decades, dried blood spots have been the standard specimen for NBS. The procedure of blood collection is well described and standardized and includes many critical pre-analytical steps. We examined the impact of contamination of some anticipated common substances on NBS results obtained from dry spot samples. This possible pre-analytical source of uncertainty has been poorly examined in the past...

The advent of mass spectrometry into the clinical laboratory has led to an improvement in clinical management of several endocrine diseases. Liquid chromatography tandem mass spectrometry found some of its first clinical applications in the diagnosis of inborn errors of metabolism, in quantitative steroid analysis, and in drug analysis laboratories. Mass spectrometry assays offer analytical sensitivity and specificity that is superior to immunoassays for many analytes. This article highlights several areas of clinical endocrinology that have witnessed the use of liquid chromatography tandem mass spectrometry to improve clinical outcomes...

The discovery that a natural product leptospermone had herbicidal activity formed the starting point for chemical synthesis to find more activity and selectivity. A series of molecules called triketones were found to possess good activity and 2-(2-nitro-4-trifluoromethylbenzoyl)-cyclohexane-1,3-dione (NTBC) was selected for toxicology testing. NTBC fed at low doses to rats and dogs caused keratopathy, which on cessation of the diet recovered. Mice, rabbits and monkeys fed NTBC did not show this response. Research discovered that NTBC caused tyrosinaemia which was due to inhibition of the enzyme 4-hydroxyphenylpyruvate dioxygenase in both mammals and plants thereby finding a novel target for killing plants...

Hereditary tyrosinemia type 1 (HT1, OMIM 276700) is a rare autosomal recessively inherited inborn error of metabolism in the tyrosine catabolic pathway due to deficiency of the enzyme fumarylacetoacetate hydrolase. The clinical features of HT1 are widely heterogenous even within the same family members. Clinical features includes acute or chronic liver disease with increased risk of hepatocellular carcinoma, hypophosphatemic rickets due to renal tubular dysfunction, glomerulosclerosis, failure to thrive, neurological porphyria-like crisis, hypertrophic cardiomyopathy and hypoglycemia due to hyperinsulinism...

Inborn errors of metabolism (IEMs) are a group of diseases involving a genetic defect that alters a metabolic pathway and that presents usually during infancy. The tyrosine degradation pathway contains five enzymes, four of which being associated with IEMs. The most severe metabolic disorder associated with this catabolic pathway is hereditary tyrosinemia type 1 (HT1; OMIM 276700). HT1 is an autosomal recessive disease caused by a deficiency of fumarylacetoacetate hydrolase (FAH), the last enzyme of the tyrosine catabolic pathway...

BACKGROUND: A baby girl was born at 39 weeks gestation to consanguineous Asian parents. From day 1 of life she had severe hypoglycaemia with an inappropriately elevated insulin concentration consistent with congenital hyperinsulinism (CHI), confirmed by the finding of a homozygous mutation in ABCC8 (encoding the sulfonylurea receptor 1). CASE DIAGNOSIS/TREATMENT: Urine organic acid analysis showed an incidentally elevated excretion of glycolate. Whilst this was unlikely to contribute to the hypoglycaemia, hyperglycolic aciduria is a known feature of primary hyperoxaluria type 1 (PH1); therefore oxalate was also measured in urine and found to be elevated...

BACKGROUND: The biological diagnosis of sphingolipidoses currently relies on the measurement of specific enzymatic activities and/or genetic studies. Lysosphingolipids have recently emerged as potential biomarkers of sphingolipidoses and Niemann-Pick type C in plasma. METHODOLOGY: We developed a sensitive and specific method enabling the simultaneous quantification of lysosphingolipids by LC-MS/MS: lysoglobotriaosylceramide for Fabry disease, lysohexosylceramide (i...

PurposeSLC39A8 deficiency is a severe inborn error of metabolism that is caused by impaired function of manganese metabolism in humans. Mutations in SLC39A8 lead to impaired function of the manganese transporter ZIP8 and thus manganese deficiency. Due to the important role of Mn(2+) as a cofactor for a variety of enzymes, the resulting phenotype is complex and severe. The manganese-dependence of β-1,4-galactosyltransferases leads to secondary hypoglycosylation, making SLC39A8 deficiency both a disorder of trace element metabolism and a congenital disorder of glycosylation...

Hypophosphatasia (HPP) is a rare inborn error of metabolism due to a loss-of-function mutation in the gene for tissue nonspecific isoenzyme of alkaline phosphatase (ALP) that results in low levels of ALP. The clinical presentation of HPP is variable and in adults can easily be misdiagnosed as other forms of osteomalacia. We present a case of a 53-year-old Caucasian female who was evaluated for recurrent metatarsal fractures. She reported her first metatarsal fracture at age 21, and since then had at least 8 more metatarsal fractures over her lifetime, most without injury other than weight bearing...