Glutaric Acidemia Type 1-Clinico-Molecular Profile and Novel Mutations in GCDH Gene in Indian Patients

Biochemical and molecular features of chinese patients with glutaric acidemia type 1 from Fujian Province, southeastern China

BACKGROUND

Glutaric acidemia type 1 (GA1) is a rare autosomal recessive inherited metabolic disorder caused by variants in the gene encoding the enzyme glutaryl-CoA dehydrogenase (GCDH). The estimated prevalence of GA1 and the mutational spectrum of the GCDH gene vary widely according to race and region. The aim of this study was to assess the acylcarnitine profiles and genetic characteristics of patients with GA1 in Fujian Province, southeastern China.

RESULTS

From January 2014 to December 2022, a total of 1,151,069 newborns (631,016 males and 520,053 females) were screened using MS/MS in six newborn screening (NBS) centers in Fujian Province and recruited for this study. Through NBS, 18 newborns (13 females and 5 males) were diagnosed with GA1. Thus, the estimated incidence of GA1 was 1 in 63,948 newborns in Fujian province. In addition, 17 patients with GA1 were recruited after clinical diagnosis. All but one patient with GA1 had a remarkable increase in glutarylcarnitine (C5DC) concentrations. The results of urinary organic acid analyses in 33 patients showed that the concentration of glutaric acid (GA) increased in all patients. The levels of C5DC and GA in patients identified via NBS were higher than those in patients identified via clinical diagnosis (P < 0.05). A total of 71 variants of 70 alleles were detected in patients with GA1, with 19 different pathogenic variants identified. The three most prevalent variants represented 73.23% of the total and were c.1244-2 A > C, p.(?) (63.38%), c.1261G > A, p.Ala421Thr (5.63%), and c.406G > T, p.Gly136Cys (4.22%). The most abundant genotype observed was c.[1244-2 A > C]; [1244-2 A > C] (18/35, 52.43%) and its phenotype corresponded to high excretors (HE, GA > 100 mmol/mol Cr).

CONCLUSIONS

In conclusion, we investigated the biochemical and molecular features of 35 unrelated patients with GA1. C5DC concentrations in dried blood spots and urinary GA are effective indicators for a GA1 diagnosis. Our study also identified a GCDH variant spectrum in patients with GA1 from Fujian Province, southeastern China. Correlation analysis between genotypes and phenotypes provides preliminary and valuable information for genetic counseling and management.

Recommendations for diagnosing and managing individuals with glutaric aciduria type 1: Third revision

Glutaric aciduria type 1 is a rare inherited neurometabolic disorder of lysine metabolism caused by pathogenic gene variations in GCDH (cytogenic location: 19p13.13), resulting in deficiency of mitochondrial glutaryl-CoA dehydrogenase (GCDH) and, consequently, accumulation of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid and glutarylcarnitine detectable by gas chromatography/mass spectrometry (organic acids) and tandem mass spectrometry (acylcarnitines). Depending on residual GCDH activity, biochemical high and low excreting phenotypes have been defined. Most untreated individuals present with acute onset of striatal damage before age 3 (to 6) years, precipitated by infectious diseases, fever or surgery, resulting in irreversible, mostly dystonic movement disorder with limited life expectancy. In some patients, striatal damage develops insidiously. In recent years, the clinical phenotype has been extended by the finding of extrastriatal abnormalities and cognitive dysfunction, preferably in the high excreter group, as well as chronic kidney failure. Newborn screening is the prerequisite for pre-symptomatic start of metabolic treatment with low lysine diet, carnitine supplementation and intensified emergency treatment during catabolic episodes, which, in combination, have substantially improved neurologic outcome. In contrast, start of treatment after onset of symptoms cannot reverse existing motor dysfunction caused by striatal damage. Dietary treatment can be relaxed after the vulnerable period for striatal damage, that is, age 6 years. However, impact of dietary relaxation on long-term outcomes is still unclear. This third revision of evidence-based recommendations aims to re-evaluate previous recommendations (Boy et al., J Inherit Metab Dis, 2017;40(1):75-101; Kolker et al., J Inherit Metab Dis 2011;34(3):677-694; Kolker et al., J Inherit Metab Dis, 2007;30(1):5-22) and to implement new research findings on the evolving phenotypic diversity as well as the impact of non-interventional variables and treatment quality on clinical outcomes.

Identification of novel pathogenic variants in the GCDH gene and assessment of neurodevelopmental outcomes in 24 children with glutaric aciduria type 1

AIM

To evaluate the pathogenic variants in GCDH gene and to assess the neurodevelopmental outcomes in children with Glutaric aciduria type 1 (GA-1).

METHOD

Cross-sectional observational study between January 2019 and June 2020 in consecutive North Indian children with a clinical and biochemical suspicion of GA-1. Variants in the coding regions of GCDH gene were identified through Sanger sequencing. Neurodevelopmental and quality of life assessment was done using standardized scales.

RESULTS

24 children with GA-1 were identified. The median age at diagnosis was 12 months and the median delay in diagnosis was 3 months. Genetic analysis was done in 14 cases. It revealed 12 variants (11 missense and one nonsense) from 13 patients. Most of the pathogenic variants were in exon 9 and exon 5. Three novel variants were identified in three patients: two missense variants c.169G > A (p.Glu57Lys), c.1048T > C (p.Cys350Arg) and one nonsense variant c.331C > T (p.Lys111Ter). On neurodevelopmental assessment, majority of children with GA-1 were non ambulatory (62.5%), had limited hand skills (58.3%) and impaired communication (58.3%). Overall, poor global development was noted in 43.7%. A pre-existing developmental delay was significantly associated with impaired communication skills (p = 0.03), and the number of episodes of encephalopathy were significantly associated with impaired gross motor skill (p = 0.02). Presence of encephalopathy was significantly associated with poor performance in social emotional (p = 0.01) and cognitive (p = 0.03) domains of Developmental Profile-III scale and development of severe dystonia (p = 0.01).

CONCLUSION

Our findings highlight the clinical, biochemical, radiological and genetic spectrum of GA-1 in children in North India and report the presence of novel pathogenic variations.

Clinical Characteristics, Molecular Profile, and Outcomes in Indian Patients with Glutaric Aciduria Type 1

Glutaric acidemia type 1 (GA-1, OMIM 231670) is an autosomal recessive inborn error of metabolism caused by the deficiency of glutaryl-coenzyme A (CoA) dehydrogenase with most children presenting in infancy with encephalopathy, dystonia, and macrocephaly. In this article, we presented the clinical characteristics, molecular profile, and outcomes in 29 unrelated families with affected children (30 cases total). The mean age at onset of illness was 10 months (±14.58), whereas the mean age at referral for molecular diagnosis was 29.44 months (±28.11). Patients were residents of nine different states of India. Clinical presentation varied from acute encephalitis followed by neuroregression and chronic/insidious developmental delay. Neurological sequelae varied from asymptomatic (no sequelae, 2 patients) to moderate (5 patients) and severe (23 patients) sequelae. All patients underwent blood tandem mass spectrometry (TMS on dried blood spots) and/or urine gas chromatography mass spectrometry (GCMS). Neuroimaging demonstrated batwing appearance in 95% cases. Sanger's sequencing of GCDH , covering all exons and exon-intron boundaries, was performed for all patients. Variants identified include 15 novel coding variants: p.Met100Thr, p.Gly107Ser, p.Leu179Val, p.Pro217Ser, p. Phe236Leufs*107, p.Ser255Pro, p.Met266Leufs*2, p.Gln330Ter, p.Thr344Ile, p.Leu345Pro, p.Lys377Arg, p.Leu424Pro, p.Asn373Lys, p.Lys377Arg, p.Asn392Metfs*9, and nine known genetic variants such as p.Arg128Gln, p.Leu179Arg, p.Trp225Ter, p.Met339Val, p.Gly354Ser, p.Arg402Gln, p.Arg402Trp, p.His403Tyr, and p.Ala433Val (Ensembl transcript ID: ENST00000222214). Using in silico analysis, genetic variants were shown to be affecting the residues responsible for homotetramer formation of the glutaryl-CoA dehydrogenase protein. Treatment included oral carnitine, riboflavin, protein-restricted diet, lysine-deficient special formulae, and management of acute crises with intravenous glucose and hydration. However, the mortality (9/30, 27.58%) and morbidity was high in our cohort with only two patients affording the diet. Our study is the largest multicentric, genetic variant-proven series of glutaric aciduria type 1 from India till date.

A novel mutation in the glutaryl-CoA dehydrogenase gene (GCDH) in an Iranian patient affected with Glutaric acidemia type 1

Our findings revealed the mutation c.536T>C (p. Leu179Pro) in GCDH gene although has not been reported so far, but the in-silico analysis and clinical symptoms of the patient indicated that the mutation is pathogenic full stop. Also, it can be diagnosed and prevented in families affected by the disease.

Low excretor glutaric aciduria type 1 of insidious onset with dystonia and atypical clinical features, a diagnostic dilemma

A 4-year-old girl was referred for reassessment of dyskinetic cerebral palsy. Initial investigations in her country of birth, India, had not yielded a diagnosis. MRI brain in infancy revealed bilateral putamen hyperintensity. She had generalized dyskinesia predominantly bulbar and limbs. Motor and speech development were most affected with preservation of cognitive development. There was no history of acute encephalopathic crisis or status dystonicus. Initial urine organic acids and amino acids and acylcarnitine profile (ACP) were normal. A dystonia genetic panel showed compound heterozygosity with a pathogenic variant and a variant of uncertain significance in the GCDH gene. The latter is hitherto undescribed and is indicative of a potential diagnosis of glutaric aciduria type 1 (alternatively glutaric acidemia type 1) (GA-1), an autosomal recessive disorder of mitochondrial lysine/hydroxylysine and tryptophan metabolism. Repeat urine organic acids showed isolated slightly increased 3-hydroxy glutarate excretion consistent with GA-1 and characterizing the patient as a "low excretor," a diagnostic sub-group where diagnosis is more challenging but prognosis is similar. Repeat MRI Brain at age 4 showed volume loss and symmetric T2 hyperintensity in the posterior putamina bilaterally. This case highlights the diagnostic dilemma of GA-1 where differing clinical courses, genetic variants, neuroradiological findings, and biochemical excretion patterns may lead to a later diagnosis. The presence of newborn screening for GA-1 should not dull the clinician's suspicion of the possibility that GA-1 may present with a complex movement disorder. Timely diagnosis and treatment is essential, as neurological sequelae are largely irreversible.

Pediatric Glutaric Aciduria Type 1: 14 Cases, Diagnosis and Management

Introduction

Glutaric aciduria type I is an autosomal recessive disorder of lysine metabolism due to the defect of the enzyme glutaryl-CoA dehydrogenase. The regression of milestones following an intercurrent infection with disabling dystonia is the common presentation. We report the clinical features, diagnosis, and management of 14 south Indian children with glutaric aciduria type I.

Results

Males predominated the study (57.1%). The mean age of onset of the symptoms was 8.57 ± 3.57 months. The mean age at the time of diagnosis was 35.21 ± 48.31 months. The history of consanguinity was noted in 57.1%. Development was normal prior to the onset of acute crises in nearly three fourths. Acute crises triggered by infection followed by the regression of milestones was the major presenting feature in 10 children (71.4%). Macrocephaly was another prominent feature in an equal number. Bat's wing appearance (fronto temporal atrophy) was present in all children. Nearly 80% had moderate to severe disability in the form of dystonic movement disorder and spastic quadriparesis.

Conclusion

Glutaric aciduria type Ihas to be identified and managed early to have a better outcome.

Is Expanded Newborn Screening Adequate to Detect Indian Biochemical Low Excretor Phenotype Patients of Glutaric Aciduria Type I?

OBJECTIVE

To investigate if expanded newborn screening using tandem mass spectroscopy (TMS) is adequate to detect low excretor phenotype in Indian Glutaric aciduria type I (GA-I) patients.

METHODS

Ten GA-I patients were investigated for blood glutaryl carnitine (C5DC) levels on dried blood spot (DBS) by tandem mass spectroscopy and urine glutaric acid (GA) and 3-hydroxyglutaric acid (3-OH-GA) by gas chromatography-mass spectroscopy. The student's T test and Pearson's correlation were applied to draw a relationship between various biochemical parameters. Further confirmation of low excretors by DNA mutation analysis in the glutaryl CoA dehydrogenase (GCDH) gene was performed by polymerase chain reaction and Sangers sequencing.

RESULTS

Among 10 GA-I patients, 7 patients were found to have high excretor, and 3 were found to have low excretor phenotype. The low excretors were found to have GCDH gene mutations. The mean C5DC levels in high and low excretors were 2.61 ± 2.02 μmol/L and 2.31 ± 1.00 μmol/L, respectively. In high excretors, C5DC levels correlated with GA (r = 0.95). In low excretors, C5DC levels correlated with 3-OH-GA (r = 0.99). No significant difference was found between C5DC levels of high and low excretors (p = 0.82).

CONCLUSIONS

The MS/MS, C5DC screening is a sensitive technique and detected 10 GA-I patients. Irrespective of the urine organic acid levels, Indian GA-I patients including low excretors seem to have a significantly elevated C5DC level and well above the stipulated cut-off values and therefore, expanded newborn screening is probably adequate to diagnose them.

Clinical, biochemical, neuroradiological and molecular characterization of Egyptian patients with glutaric acidemia type 1

Glutaric acidemia type 1 (GA1) is an inherited metabolic autosomal recessive disorder that is caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Untreated patients suffer primarily from severe striatal damage. More than 250 variants in the GCDH gene have been reported with a variable frequency among different ethnic groups. In this study, we aimed to characterize 89 Egyptian patients with GA1 and identify the variants in the 41 patients who were available for genotyping. All of our patients demonstrated clinical, neuroradiological, and biochemical characteristics that are consistent with a diagnosis of GA1. All patients presented with variable degrees of developmental delay ranging from mild to severe. Most of the 89 patients presented with acute onset type (71.9%), followed by insidious (19%) and asymptomatic (9%). A delay in diagnosis was inversely associated with macrocephaly. The prevalence rate ratio (PR) for macrocephaly that was associated with each 6-month delay was 0.95 (95%CI 0.91-0.99). However, high body weight was associated with a higher likelihood of having macrocephaly (PR 1.16, 95%CI 1.06-1.26 per 1 SD increment of Z score weight). However, body weight was inversely associated with the morbidity score. Consanguinity level was 64% among our patient's cohort and was positively associated with the C5DC level (β (95%CI) 1.06 (0.12-1.99)). Forty-one patients were available for genotyping and were sequenced for the GCDH gene. We identified a total of 25 variants, of which the following six novel variants were identified: three missense variants, c.320G > T (p.Gly107Val), c.481C > T (p.Arg161Trp) and c.572 T > G (p.Met191Arg); two deletions, c.78delG (p.Ala27Argfs34) and c.1035delG (p.Gly346Alafs*11); and one indel, c.272_331del (p.Val91_Lys111delinsGlu). All of the novel variants were absent in the 300 normal chromosomes. The most common variant, c.*165A > G, was detected in 42 alleles, and the most commonly detected missense variant, c.1204C > T (p.Arg402Trp), was identified in 29 mutated alleles in 15/41 (34.2%) of patients. Our findings suggest that GA1 is not uncommon organic acidemia disease in Egypt; therefore, there is a need for supporting neonatal screening programs in Egypt.

Genotype-phenotype correlation in 18 Egyptian patients with glutaric acidemia type I

Glutaric acidemia I (GAI) is an autosomal recessive metabolic disease caused by a deficiency of glutaryl-CoA dehydrogenase enzyme (GCDH). Patients with GAI are characterized by macrocephaly, acute encephalitis-like crises, dystonia and frontotemporal atrophy. In this study, we investigated 18 Egyptian patients that were diagnosed with GAI based on their clinical, neuroradiological, and biochemical profiles. Of the 18 patients, 16 had developmental delay and/or regression, dystonia was prominent in 75% of the cases, and three patients died. Molecular genetics analysis identified 14 different mutations in the GCDH gene in the 18 patients, of the 14 mutations, nine were missense, three were in the 3'-Untranslated Region (3'-UTR), one was nonsense, and one was a silent mutation. Four novel mutations were identified (c.148 T > A; p.Trp50Arg, c.158C > A; p.Pro53Gln, c.1284C > G; p.Ile428Met, and c.1189G > T; p.Glu397*) that were all absent in 300 normal chromosomes. The 3'-UTR mutation (c.*165A > G; rs8012), was the most frequent mutation observed (0.5; 18/36), followed by the most common mutation among Caucasian patients (p.Arg402Trp; rs121434369) with allele frequency of 0.36 (13/36), and the 3'-UTR mutation (c.*288G > T; rs9384, 0.22; 8/16). The p.Arg257Gln mutation was found with allele frequency of ~0.17 (6/36). The marked homozygosity observed in our patients is probably due to the high level of consanguinity that is observed in 100% of the cases. We used nine in silico prediction tools to predict the pathogenicity (SIFT, PhD-SNP, SNAP, Meta-SNP, PolyPhen2, and Align GVGD) and protein stability (I-Mutant2.0, Mupro, and istable) of the nine missense mutants. The mutant p.Arg402Trp was predicted to be most deleterious by all the six pathogenicity prediction tools and destabilizing by all the three-stability prediction tools, and highly conserved by the ConSurf server. Using the clinical, biochemical, family history of the 18 patients, and the in silico analysis of the missense mutations, our study showed a mix of conclusive and inconclusive genotype-phenotype correlations among our patient's cohort and suggests the usefulness of using various sophisticated computational analysis to be utilized for future variant classifications in the genetic clinics.

Genetic Screening of Selected Disease-Causing Mutations in Glutaryl-CoA Dehydrogenase Gene among Indian Patients with Glutaric Aciduria Type I

Glutaric aciduria type I (GA-I) is an organic aciduria caused by glutaryl-CoA dehydrogenase (GCDH) deficiency. There are limited studies on GA-I from India. A total of 48 Indian GA-I patients were screened for selected disease-causing mutations such as R402W, A421V, A293T, R227P, and V400M using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Among these patients, 9 (18.8%) had R402W mutation, and none had A421V, A293T, R227P, or V400M mutation. One low excretor mutation (P286S) and several novel mutations (I152M, Q144P, and E414X) were also found in this study. We conclude that among selected mutations, R402W is the most common mutation found among Indian GA-I patients.

Glutaric Acidemia Type 1: A Case of Infantile Stroke

BACKGROUND

Glutaric acidemia Type 1 (GA-1) is an autosomal recessively inherited metabolic disorder which is associated with GCDH gene mutations which alters the glutaryl-CoA dehydrogenase, an enzyme playing role in the catabolic pathways of the amino acids lysine, hydroxylysine, and tryptophan. Clinical findings are often encephalopathic crises, dystonia, and extrapyramidal symptoms.

CASE REPORT

A 9-month-old male infant referred to our department with focal tonic-clonic seizures during rotavirus infection and acute infarcts in MRI. Clinical manifestation, MRI findings, and metabolic investigations directed thoughts towards GA-I. Molecular genetic testing revealed a homozygous c.572T>C (p.M191T) mutation in GCDH gene which confirmed the diagnosis. Application of protein restricted diet, carnitine and riboflavin supplementations prevented the progression of Magnetic Resonance Imaging (MRI) and clinical pathologic findings during the 1 year of follow-up period.

CONCLUSION

This case is of great importance since it shows possibility of infantile stroke in GA-1, significance of early diagnosis and phenotypic variability of disease.

Severe neurological manifestations in an Egyptian patient with a novel frameshift mutation in the Glutaryl-CoA dehydrogenase gene

To characterize an Egyptian patient with glutaric acidemia type I (GA I) and to identify the causative mutation(s) that may be responsible for the disease phenotype. MRI was performed on the patient using the 1.5 T magnet, biochemical analysis was carried out using gas chromatography/mass spectrometry on the patient's dried blood spot, and the patient's organic acids were measured in dried blood and a urine sample using MS/MS and GC/MS, respectively. Total RNA was isolated from the patient's peripheral blood, and the synthesized cDNA was bi-directionally sequenced. The patient exhibited clinical features and MRI findings compatible with a diagnosis of GA I. The abnormal elevation of organic acids in the urine supported the presence of glutaryl-CoA dehydrogenase deficiency. Gene sequencing revealed a novel homozygous frameshift mutation, c.644_645insCTCG; p.(Pro217Leufs*14), in exon 8 of the GCDH gene. The present study revealed a novel frameshift mutation responsible for a severe GA I phenotype in an Egyptian patient. This novel mutation will ultimately contribute to a better understanding of the molecular pathology of the disease and shed light on the intricacies of the genotype-phenotype correlation of GA I disease.

Proposed recommendations for diagnosing and managing individuals with glutaric aciduria type I: second revision

Glutaric aciduria type I (GA-I; synonym, glutaric acidemia type I) is a rare inherited metabolic disease caused by deficiency of glutaryl-CoA dehydrogenase located in the catabolic pathways of L-lysine, L-hydroxylysine, and L-tryptophan. The enzymatic defect results in elevated concentrations of glutaric acid, 3-hydroxyglutaric acid, glutaconic acid, and glutaryl carnitine in body tissues, which can be reliably detected by gas chromatography/mass spectrometry (organic acids) and tandem mass spectrometry (acylcarnitines). Most untreated individuals with GA-I experience acute encephalopathic crises during the first 6 years of life that are triggered by infectious diseases, febrile reaction to vaccinations, and surgery. These crises result in striatal injury and consequent dystonic movement disorder; thus, significant mortality and morbidity results. In some patients, neurologic disease may also develop without clinically apparent crises at any age. Neonatal screening for GA-I us being used in a growing number of countries worldwide and is cost effective. Metabolic treatment, consisting of low lysine diet, carnitine supplementation, and intensified emergency treatment during catabolism, is effective treatment and improves neurologic outcome in those individuals diagnosed early; treatment after symptom onset, however, is less effective. Dietary treatment is relaxed after age 6 years and should be supervised by specialized metabolic centers. The major aim of this second revision of proposed recommendations is to re-evaluate the previous recommendations (Kölker et al. J Inherit Metab Dis 30:5-22, 2007b; J Inherit Metab Dis 34:677-694, 2011) and add new research findings, relevant clinical aspects, and the perspective of affected individuals.

Glutaric AciduriaType 1: Clinical and Molecular Study in Iranian Patients, 3 Novel Mutations

OBJECTIVE

Glutaricaciduria type 1 (GA1), is a rare, treatable neuro metabolic disease, due to glutaryl- CoA dehydrogenase (GCDH) gene mutation.In regions without neonatal blood screening (NBS), patients are diagnosed in symptomatic period. This study was carried out to assess patients with GA1 for clinical, biochemical, neuroimaging findings and GCDH gene mutations analysis.

MATERIALS & METHODS

In this cross-sectional study, clinical manifestation, neuroimaging and metabolic findings of eleven Iranian GA1 patients of MofidChildren's Hospital, Tehran, Iranbetween 2001 and 2011,were evaluated.Mutational analysis of the GCDH gene was performed on genomic DNA. Genomic DNA was extracted from peripheral lymphocytes using QIAamp DNA Micro Kit (Qiagen). All 11 exons and flanking intronic regions of the GCDH gene were amplified by polymerase chain reaction (PCR).

RESULTS

All patients were diagnosed before 32 months old. Clinical presentations of GA1 include acute encephalopathic crisis and/or developmental delay and macrocephaly. Seven GCDH gene mutations were detected in our patients. The most frequent GCDH mutations occurred in exon7 then exon8, 10 and11. G244 C in exon7, R294 Q in exon8 and N373 S in exon 10 were three novel mutations. There was no correlation between of genotype and phenotype in our patients.

CONCLUSION

Physician must remember GA1 in differential diagnosis of acute encephalopathic crisis, macrocephaly, developmental delay, movement disorders such as dystonia and dyskinesia. Early detection, proper treatment and selective screening of patients' siblings can prevent neurologic disabilities.

Recurrent rhabdomyolysis and glutaric aciduria type I: a case report and literature review

BACKGROUND

Glutaric acidemia type I (GA-I) is a rare metabolic disorder caused by mutation of the glutaryl- CoA dehydrogenase (GCDH) gene. The occurrence of rhabdomyolysis with GA-I is extremely rare.

METHODS

We reported a child with recurrent rhabdomyolysis and undiagnosed glutaric acidemia type I (GA-I). And a literature review was performed.

RESULTS

A 4.5-year-old girl was admitted to our hospital due to recurrent rhabdomyolysis for 3 times within three years. At the third admission, she was diagnosed with GA-I by biochemical testing and mutation analysis. The girl was found to have a serine to leucine replacement mutation of the GCDH gene in exon 8 at position 764. Other three patients with rhabdomyolysis and GA-I were discovered by literature searching.

CONCLUSIONS

This report highlights that patients with GA-I may have an increased risk of rhabdomyolysis.

Single Lysis-Salting Out Method of Genomic DNA Extraction From Dried Blood Spots

BACKGROUND

Dried blood spots (DBS) are an important form of bio-sampling and valuable approach for storing blood samples for genetic studies. This has necessitated in developing an effective protocol to isolate genomic DNA (gDNA) from DBS samples.In this study, we have elucidated a dependable and non-hazardous "single lysis-salting out" (SLSO) protocol of gDNA extraction from DBS and compared against the available commercial kits.

METHODS

For the purpose of this study, blood spots were collected on S&S 903 filter cards from 10 healthy volunteers and 30 patients with glutaric aciduria type I (GA-I). The gDNA was extracted from theseDBS samples by SLSO, QIAamp® gDNA Micro kit and innuPREP forensic kit methods. The quantity and quality of gDNA obtained from these methods were determined by measuring the absorbance using a Nanodrop spectrophotometer.

RESULTS

The SLSO method showed four-fold and eight-fold increased yield of gDNA in healthy volunteers and patient samples, respectively, compared to commercial kits (p<0.0001). The protocol was also found to be cost efficient, reducing the per sample cost to almost half. The suitability of this method for genetic studies was confirmed by performing R402W genotyping by RFLP in GA-I patients. The genotyping results showed the presence of R402W mutation in 20% (6/30) of patients.

CONCLUSION

The SLSO method was found to be inexpensive, non-hazardous and a suitable technique for isolating gDNA from DBS samples for genetic studies.

Clinical and molecular investigation in Chinese patients with glutaric aciduria type I

Glutaric aciduria type I (GA-I) is a rare autosomal recessive metabolic disorder caused by deficiency of glutaryl-CoA dehydrogenase (GCDH), leading to an abnormal metabolism of lysine, hydroxylysine and tryptophan. It results in accumulations of glutaric acid, 3-hydroxyglutaric acid and glutaconic acid. Clinical features include the sudden onset of encephalopathy, hypotonia and macrocephaly usually before age 18months. Here we report five cases of GA-I confirmed with mutation analysis. GCDH gene mutations were identified in all five probands with GA-I. Three of them had compound heterozygous mutations and two had homozygous mutations. Mutations of two alleles (c.334G>T and IVS11-11A>G) were novel and both of them were confirmed to be splice site mutations by reverse transcription PCR.