Carnitine plays essential roles in intermediary metabolism. In non-vegetarians, most of carnitine sources (~75%) are obtained from diet whereas endogenous synthesis accounts for around 25%. Renal ...carnitine reabsorption along with dietary intake and endogenous production maintain carnitine homeostasis. The precursors for carnitine biosynthesis are lysine and methionine. The biosynthetic pathway involves four enzymes: 6-
-trimethyllysine dioxygenase (TMLD), 3-hydroxy-6-
-trimethyllysine aldolase (HTMLA), 4-
-trimethylaminobutyraldehyde dehydrogenase (TMABADH), and γ-butyrobetaine dioxygenase (BBD). OCTN2 (organic cation/carnitine transporter novel type 2) transports carnitine into the cells. One of the major functions of carnitine is shuttling long-chain fatty acids across the mitochondrial membrane from the cytosol into the mitochondrial matrix for β-oxidation. This transport is achieved by mitochondrial carnitine-acylcarnitine cycle, which consists of three enzymes: carnitine palmitoyltransferase I (CPT I), carnitine-acylcarnitine translocase (CACT), and carnitine palmitoyltransferase II (CPT II). Carnitine inborn errors of metabolism could result from defects in carnitine biosynthesis, carnitine transport, or mitochondrial carnitine-acylcarnitine cycle. The presentation of these disorders is variable but common findings include hypoketotic hypoglycemia, cardio(myopathy), and liver disease. In this review, the metabolism and homeostasis of carnitine are discussed. Then we present details of different inborn errors of carnitine metabolism, including clinical presentation, diagnosis, and treatment options. At the end, we discuss some of the causes of secondary carnitine deficiency.
PKU is an autosomal recessive hereditary inborn error of metabolism caused by a lack of phenylalanine hydroxylase enzyme activity. Pegvaliase (PALYNZIQ®) treatment has been approved to reduce blood ...Phe concentrations in adult phenylketonuria patients with uncontrolled blood Phe concentrations greater than 600 micromol/L on current management. However, data regarding individuals under the age of 16 is still unavailable.
We report a 12-year-old Saudi girl who underwent pegvaliase therapy and was closely monitored for one year. Remarkably, a positive therapeutic response became apparent six months after commencing pegvaliase treatment. Phenylalanine (Phe) levels showed significant improvement, stabilising within the < 5 to 14 µmol/L range on a regular diet without any restriction. At her current age of 12, the patient maintains an unrestricted dietary regimen, consuming a diverse selection of foods, including poultry, meat, and protein sources, all while consistently maintaining normal Phe levels with no change in mental status after treatment. The parents gave their written, informed consent in allowing the research study to be carried out and clinical data to be published.
This report addresses the potential broader applications of Pegvaliase in children, as well as its safety and tolerability in this age group. However, larger sample sizes and robust methodologies are required to validate such findings.
Polydactyly, also known as
or
is the most common hereditary limb anomaly characterized by extra fingers or toes, with various associated morphologic phenotypes as part of a syndrome (syndromic ...polydactyly) or may occur as a separate event (non-syndromic polydactyly). Broadly, the non-syndromic polydactyly has been classified into three types, i.e.; preaxial polydactyly (radial), central polydactyly (axial), and postaxial polydactyly (ulnar). Mostly inherited as an autosomal dominant entity with variable penetrance and caused by defects that occur in the anterior-posterior patterning of limb development. In humans, to-date at least 10 loci and six genes causing non-syndromic polydactyly have been identified, including the
,
,
,
,
, and the
. In the present review, clinical, genetic and molecular characterization of the polydactyly types has been presented including the recent genes and loci identified for non-syndromic polydactyly. This review provides an overview of the complex genetic mechanism underlie polydactyly and might help in genetic counseling and quick molecular diagnosis.
Solute carrier family 19 (thiamine transporter), member 3 (SCL19A3) gene defect produces an autosomal recessive neurodegenerative disorder associated with different phenotypes and acronyms. One of ...the common presentations is early infantile lethal Leigh-like syndrome. We report a case of early infantile Leigh-like SLC19A3 gene defects of patients who died at 4 months of age with no response to a high dose of biotin and thiamine. In addition, we report a novel mutation that was not reported previously. Finally, we review the literature regarding early infantile Leigh-like SLC19A3 gene defects and compare the literature with our patient.
Multiple mitochondrial dysfunctions syndrome 4, caused by ISCA2 gene defects (OMIM #616370), was first described by Al-Hassnan et al in 2015. To date, 20 cases have been reported: 13 females and 7 ...males from 18 different families. All cases are from Saudi Arabia except those from one Italian family. Typically, the patients have normal antenatal and birth history and attain normal development initially. Rapid deterioration occurs between 2 and 7 months of age, with the triad of neurodevelopmental regression, optic atrophy with nystagmus, and diffuse white matter disease. Magnetic resonance imaging findings include 75% of patients have cerebellar white matter abnormalities, and the spinal cord was affected in 55%. Magnetic resonance spectroscopy showed elevated glycine peaks in 2 (10%) cases and elevated lactate peaks in 5 (25%) cases. Biochemical abnormalities include high cerebrospinal fluid glycine and lactate and high plasma glycine and lactate, but these findings were not consistent. Diagnosis is based on the detection of biallelic mutations in the ISCA2 gene. To date, no curative treatment has been discovered, and disease management is exclusively supportive. In this report, the authors review the published cases of ISCA2 gene defects and retrospectively characterize disease phenotypes, the affected biochemical pathways, neuroradiological abnormalities, diagnosis, genetics, and treatment.
Spondylocostal dysostosis is a genetic defect associated with severe rib and vertebrae malformations. In recent years, extensive clinical and molecular diagnosis advancements enabled us to identify ...disease-causing variants in different genes for such severe conditions. The identification of novel candidate genes enabled us to understand the developmental biology and molecular and cellular mechanisms involved in the etiology of these rare diseases. Here, we discuss the clinical and molecular targets associated with spondylocostal dysostosis, including clinical evaluation, genes, and pathways involved. This review might help us understand the basics of such a severe disorder, which might help in proper clinical characterization and help in future therapeutic strategies.
Abstract
DCBLD
2 encodes discodin, CUB and LCCL domain-containing protein 2, a type-I transmembrane receptor that is involved in intracellular receptor signalling pathways and the regulation of cell ...growth. In this report, we describe a 5-year-old female who presented severe clinical features, including restrictive cardiomyopathy, developmental delay, spasticity and dysmorphic features. Trio-whole-exome sequencing and segregation analysis were performed to identify the genetic cause of the disease within the family. A novel homozygous nonsense variant in the
DCBLD2
gene (c.80G > A, p.W27*) was identified as the most likely cause of the patient’s phenotype. This nonsense variant falls in the extracellular N-terminus of
DCBLD2
and thus might affect proper protein function of the transmembrane receptor. A number of in vitro investigations were performed on the proband’s skin fibroblasts compared to normal fibroblasts, which allowed a comprehensive assessment resulting in the functional characterization of the identified
DCBLD2
nonsense variant in different cellular processes. Our data propose a significant association between the identified variant and the observed reduction in cell proliferation, cell cycle progression, intracellular ROS, and Ca2 + levels, which would likely explain the phenotypic presentation of the patient as associated with lethal restrictive cardiomyopathy.
Despite clear technical superiority of genome sequencing (GS) over other diagnostic methods such as exome sequencing (ES), few studies are available regarding the advantages of its clinical ...application. We analyzed 1007 consecutive index cases for whom GS was performed in a diagnostic setting over a 2-year period. We reported pathogenic and likely pathogenic (P/LP) variants that explain the patients' phenotype in 212 of the 1007 cases (21.1%). In 245 additional cases (24.3%), a variant of unknown significance (VUS) related to the phenotype was reported. We especially investigated patients which had had ES with no genetic diagnosis (n = 358). For this group, GS diagnostic yield was 14.5% (52 patients with P/LP out of 358). GS should be especially indicated for ES-negative cases since up to 29.6% of them could benefit from GS testing (14.5% with P/LP, n = 52 and 15.1% with VUS, n = 54). Genetic diagnoses in most of the ES-negative/GS-positive cases were determined by technical superiority of GS, i.e., access to noncoding regions and more uniform coverage. Importantly, we reported 79 noncoding variants, of which, 41 variants were classified as P/LP. Interpretation of noncoding variants remains challenging, and in many cases, complementary methods based on direct enzyme assessment, biomarker testing and RNA analysis are needed for variant classification and diagnosis. We present the largest cohort of patients with GS performed in a clinical setting to date. The results of this study should direct the decision for GS as standard second-line, or even first-line stand-alone test.
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