glutaric aciduria type i ( ga - i ) is a rare autosomal recessive disease with abnormalities in organic acid metabolism , and is caused by the functional defects of glutaryl - coa dehydrogenase ( gcdh ) , which results in metabolic disorders of lysine , hydroxylysine and tryptophan , leading to the excessive accumulation of bypass metabolites , such as glutaric acid , 3-hydroxy - glutaric acid and other toxic substances . this results in an increase in urine levels of glutaric acid and 3-hydroxy - glutaric acid ( 1 ) . it has been reported that the incidence rate of ga - i is ~1:100,000 ( 2 ) . approximately 90% of patients develop ga - i in early childhood , and the remaining 10% of patients show mild symptoms or no symptoms ( 3 ) . in recent years , ga - i in the chinese population has gained increasing interest ( 47 ) . however , a large number of children do not receive a timely diagnosis and proper treatment clinically . therefore , further research is required in order to determine the incidence of ga - i in chinese children . the present study collected and analyzed the clinical , biochemical , neuroimaging and genetic mutation information of two patients with ga - i in one uighur family , admitted to the department of pediatrics , the first hospital of xinjiang medical university ( urumqi , china ) in 2014 . the study was conducted in accordance with the declaration of helsinki , and received approval from the ethics committee of xinjiang medical university . written informed consent was obtained from all participants . a 12-year - old uighur girl from xinjiang , china , was admitted to the department of pediatrics , the first affiliated hospital of xinjiang medical university in october 2014 for an intermittent headache ( 0.52 h in duration ) over a period of 2 months . the headache typically occurred once every 35 days , with no increasing or decreasing trend . hospital examination revealed that blood glucose , creatine kinase , blood lactate and alanine transaminase levels were within normal ranges . outpatient cranial magnetic resonance imaging ( mri ) revealed white matter degeneration . as a result , a diagnosis of encephalitis or inherited metabolic disease was considered . regarding previous disease history , the patient exhibited normal growth and development , intelligence , vision and hearing , but exhibited poor physical strength and endurance since childhood , could not tolerate hunger , and had no particular bad habits . cheek skin exhibited a scattered red rash , and cranial nerve examination revealed no abnormalities . the muscle strength of the bi - upper and bi - lower limbs was grade 5 in the mrc scale ( 8) ; the muscle tonus of the four limbs was normal , with normal tendon reflexes in the upper and lower limbs . no bilateral pathological signs were detected , and the body 's superficial sensation examinations were normal . cranial mri showed bilateral temporal lobe arachnoid cyst , focal patchy t2 flair high signals in semi - oval area , corner and anteroposterior horns of the lateral ventricle , indicating white matter degeneration ( figs . 1 and 2 ) . the figures were captured at two month intervals , and no significant change was identified . a 6-year - old uighur girl from xinjiang was the sister of case 1 , and presented with no clinical symptoms . physical examination and imaging tests showed no abnormalities . tandem mass spectrometry ( ms / ms ) and gas chromatography / mass spectrometry ( gc / ms ) were used to analyze blood acylcarnitine and urine organic acids in the patient with suspected ga - i . to detect blood acylcarnitine and amino acids by ms / ms , venous blood was sampled , dripped onto special filter paper , and sent for detection after drying . an ms / ms instrument ( api 2,000 ; applied biosystems ; thermo fisher scientific , inc . , waltham , ma , usa ) was used for the testing . for the detection of organic acids by gc / ms , urine samples were treated with urease , hydrochloric acid hydroxylammonium , sodium hydroxide and hydrochloric acid , and a gc / ms instrument ( qp2010 ; shimadzu corporation , kyoto , japan ) for detection . the results of ms / ms and gc / ms detection are presented in tables i  iii . urinary glutaric acid and 3-hydroxy - glutaric acid in the two patients were increased , and glutaric acid levels were increased by 2,510.08- and 1,172.28-fold compared with the normal reference value ( 04 ) , in cases 1 and 2 , respectively . levels of 3-hydroxy glutaric acid were increased by 22.58- and 12.19-fold compared with the normal reference value ( 0 ) ( tables i and ii ) in cases 1 and 2 , respectively . blood acylcarnitine analysis showed that glutaryl carnitine in the cases 1 and 2 was increased by 0.8 and 1.177 moll , respectively ( normal reference value , 00.20 moll ) , while free acylcarnitine in the two patients was markedly reduced by 7.887 and 6.011 moll , respectively ( normal reference value , 1060 moll ) ( table iii ) . the test results of arylsulfatase a and galactocerebroside esterase of cases 1 and 2 were both within the normal ranges , 170.8 and 31.0 nmol/17 h / mgpr ; 152.4 and 27.6 nmol/17 h / mgpr , respectively ( reference values , 134.1325.1 nmol/17 h / mgpr and 19.068.2 nmol/17 h / mgpr , respectively ) . as a result , a diagnosis of leukodystrophy could be excluded ( table iv ) . genetic analysis of gcdh in the two patients and their parents was performed by gene dna sequencing . polymerase chain reaction amplified all exons and para - intronic regions of gcdh , and a dna automatic analyzer was used to analyze the amplification products . two mutations were detected in the patients : loci c. 1204c > t , p.r402w , heterozygous mutation , originating from the father ; and c. 532 g > a , p.g178r , heterozygous mutation , originating from the mother . these two mutations had been previously reported , and were considered as the pathogenic mutations ( 9,10 ) . electromyography showed no abnormalities in any muscles ( bi - rectus femoris and bi - gastrocnemius ) . in conclusion , after the diagnosis of ga - i was confirmed by ms , no muscle biopsy was performed according to patients ' wishes . the patients were administered a low - fat , low - protein and high - carbohydrate diet , and large doses of vitamin b2 ( 50 mg , tid ) and l - carnitine ( 100 mg / kg / day ) were supplemented for symptomatic treatment . the headache symptom in case 1 disappeared , and follow - up review showed that lactic acid , enzymes and liver functions were all within normal ranges . the follow - up was lasted for two months , and the patients expressed no clinical symptoms within that period . a 12-year - old uighur girl from xinjiang , china , was admitted to the department of pediatrics , the first affiliated hospital of xinjiang medical university in october 2014 for an intermittent headache ( 0.52 h in duration ) over a period of 2 months . the headache typically occurred once every 35 days , with no increasing or decreasing trend . hospital examination revealed that blood glucose , creatine kinase , blood lactate and alanine transaminase levels were within normal ranges . outpatient cranial magnetic resonance imaging ( mri ) revealed white matter degeneration . as a result , a diagnosis of encephalitis or inherited metabolic disease was considered . regarding previous disease history , the patient exhibited normal growth and development , intelligence , vision and hearing , but exhibited poor physical strength and endurance since childhood , could not tolerate hunger , and had no particular bad habits . cheek skin exhibited a scattered red rash , and cranial nerve examination revealed no abnormalities . the muscle strength of the bi - upper and bi - lower limbs was grade 5 in the mrc scale ( 8) ; the muscle tonus of the four limbs was normal , with normal tendon reflexes in the upper and lower limbs . no bilateral pathological signs were detected , and the body 's superficial sensation examinations were normal . cranial mri showed bilateral temporal lobe arachnoid cyst , focal patchy t2 flair high signals in semi - oval area , corner and anteroposterior horns of the lateral ventricle , indicating white matter degeneration ( figs . 1 and 2 ) . the figures were captured at two month intervals , and no significant change was identified . a 6-year - old uighur girl from xinjiang was the sister of case 1 , and presented with no clinical symptoms . physical examination and imaging tests showed no abnormalities . tandem mass spectrometry ( ms / ms ) and gas chromatography / mass spectrometry ( gc / ms ) were used to analyze blood acylcarnitine and urine organic acids in the patient with suspected ga - i . to detect blood acylcarnitine and amino acids by ms / ms , venous blood was sampled , dripped onto special filter paper , and sent for detection after drying . an ms / ms instrument ( api 2,000 ; applied biosystems ; thermo fisher scientific , inc . , waltham , ma , usa ) was used for the testing . for the detection of organic acids by gc / ms , urine samples were treated with urease , hydrochloric acid hydroxylammonium , sodium hydroxide and hydrochloric acid , and a gc / ms instrument ( qp2010 ; shimadzu corporation , kyoto , japan ) for detection . the results of ms / ms and gc / ms detection are presented in tables i  iii . urinary glutaric acid and 3-hydroxy - glutaric acid in the two patients were increased , and glutaric acid levels were increased by 2,510.08- and 1,172.28-fold compared with the normal reference value ( 04 ) , in cases 1 and 2 , respectively . levels of 3-hydroxy glutaric acid were increased by 22.58- and 12.19-fold compared with the normal reference value ( 0 ) ( tables i and ii ) in cases 1 and 2 , respectively . blood acylcarnitine analysis showed that glutaryl carnitine in the cases 1 and 2 was increased by 0.8 and 1.177 moll , respectively ( normal reference value , 00.20 moll ) , while free acylcarnitine in the two patients was markedly reduced by 7.887 and 6.011 moll , respectively ( normal reference value , 1060 moll ) ( table iii ) . the test results of arylsulfatase a and galactocerebroside esterase of cases 1 and 2 were both within the normal ranges , 170.8 and 31.0 nmol/17 h / mgpr ; 152.4 and 27.6 nmol/17 h / mgpr , respectively ( reference values , 134.1325.1 nmol/17 h / mgpr and 19.068.2 nmol/17 h / mgpr , respectively ) . as a result , a diagnosis of leukodystrophy could be excluded ( table iv ) . genetic analysis of gcdh in the two patients and their parents was performed by gene dna sequencing . polymerase chain reaction amplified all exons and para - intronic regions of gcdh , and a dna automatic analyzer was used to analyze the amplification products . two mutations were detected in the patients : loci c. 1204c > t , p.r402w , heterozygous mutation , originating from the father ; and c. 532 g > a , p.g178r , heterozygous mutation , originating from the mother . these two mutations had been previously reported , and were considered as the pathogenic mutations ( 9,10 ) . electromyography showed no abnormalities in any muscles ( bi - rectus femoris and bi - gastrocnemius ) . in conclusion , after the diagnosis of ga - i was confirmed by ms , no muscle biopsy was performed according to patients ' wishes . the patients were administered a low - fat , low - protein and high - carbohydrate diet , and large doses of vitamin b2 ( 50 mg , tid ) and l - carnitine ( 100 mg / kg / day ) were supplemented for symptomatic treatment . the headache symptom in case 1 disappeared , and follow - up review showed that lactic acid , enzymes and liver functions were all within normal ranges . the follow - up was lasted for two months , and the patients expressed no clinical symptoms within that period . a 12-year - old uighur girl from xinjiang , china , was admitted to the department of pediatrics , the first affiliated hospital of xinjiang medical university in october 2014 for an intermittent headache ( 0.52 h in duration ) over a period of 2 months . the headache typically occurred once every 35 days , with no increasing or decreasing trend . hospital examination revealed that blood glucose , creatine kinase , blood lactate and alanine transaminase levels were within normal ranges . outpatient cranial magnetic resonance imaging ( mri ) revealed white matter degeneration . as a result , a diagnosis of encephalitis or inherited metabolic disease was considered . regarding previous disease history , the patient exhibited normal growth and development , intelligence , vision and hearing , but exhibited poor physical strength and endurance since childhood , could not tolerate hunger , and had no particular bad habits . cheek skin exhibited a scattered red rash , and cranial nerve examination revealed no abnormalities . the muscle strength of the bi - upper and bi - lower limbs was grade 5 in the mrc scale ( 8) ; the muscle tonus of the four limbs was normal , with normal tendon reflexes in the upper and lower limbs . no bilateral pathological signs were detected , and the body 's superficial sensation examinations were normal . cranial mri showed bilateral temporal lobe arachnoid cyst , focal patchy t2 flair high signals in semi - oval area , corner and anteroposterior horns of the lateral ventricle , indicating white matter degeneration ( figs . 1 and 2 ) . the figures were captured at two month intervals , and no significant change was identified . a 6-year - old uighur girl from xinjiang was the sister of case 1 , and presented with no clinical symptoms . physical examination and imaging tests showed no abnormalities . tandem mass spectrometry ( ms / ms ) and gas chromatography / mass spectrometry ( gc / ms ) were used to analyze blood acylcarnitine and urine organic acids in the patient with suspected ga - i . to detect blood acylcarnitine and amino acids by ms / ms , venous blood was sampled , dripped onto special filter paper , and sent for detection after drying . an ms / ms instrument ( api 2,000 ; applied biosystems ; thermo fisher scientific , inc . , waltham , ma , usa ) was used for the testing . for the detection of organic acids by gc / ms , urine samples were treated with urease , hydrochloric acid hydroxylammonium , sodium hydroxide and hydrochloric acid , and a gc / ms instrument ( qp2010 ; shimadzu corporation , kyoto , japan ) for detection . the results of ms / ms and gc / ms detection are presented in tables i  iii . urinary glutaric acid and 3-hydroxy - glutaric acid in the two patients were increased , and glutaric acid levels were increased by 2,510.08- and 1,172.28-fold compared with the normal reference value ( 04 ) , in cases 1 and 2 , respectively . levels of 3-hydroxy glutaric acid were increased by 22.58- and 12.19-fold compared with the normal reference value ( 0 ) ( tables i and ii ) in cases 1 and 2 , respectively . blood acylcarnitine analysis showed that glutaryl carnitine in the cases 1 and 2 was increased by 0.8 and 1.177 moll , respectively ( normal reference value , 00.20 moll ) , while free acylcarnitine in the two patients was markedly reduced by 7.887 and 6.011 moll , respectively ( normal reference value , 1060 moll ) ( table iii ) . the test results of arylsulfatase a and galactocerebroside esterase of cases 1 and 2 were both within the normal ranges , 170.8 and 31.0 nmol/17 h / mgpr ; 152.4 and 27.6 nmol/17 h / mgpr , respectively ( reference values , 134.1325.1 nmol/17 h / mgpr and 19.068.2 nmol/17 h / mgpr , respectively ) . as a result , a diagnosis of leukodystrophy could be excluded ( table iv ) . genetic analysis of gcdh in the two patients and their parents was performed by gene dna sequencing . polymerase chain reaction amplified all exons and para - intronic regions of gcdh , and a dna automatic analyzer was used to analyze the amplification products . two mutations were detected in the patients : loci c. 1204c > t , p.r402w , heterozygous mutation , originating from the father ; and c. 532 g > a , p.g178r , heterozygous mutation , originating from the mother . these two mutations had been previously reported , and were considered as the pathogenic mutations ( 9,10 ) . electromyography showed no abnormalities in any muscles ( bi - rectus femoris and bi - gastrocnemius ) . in conclusion , a diagnosis of late - onset ga - i was decided for both cases . after the diagnosis of ga - i was confirmed by ms , no muscle biopsy was performed according to patients ' wishes . the patients were administered a low - fat , low - protein and high - carbohydrate diet , and large doses of vitamin b2 ( 50 mg , tid ) and l - carnitine ( 100 mg / kg / day ) were supplemented for symptomatic treatment . the headache symptom in case 1 disappeared , and follow - up review showed that lactic acid , enzymes and liver functions were all within normal ranges . the follow - up was lasted for two months , and the patients expressed no clinical symptoms within that period . ga - i is a relatively rare disease among organic aciduria that was first reported in 1975 by goodman ( 11 ) , and > 200 pathogenic mutations have been reported to date ( 12 ) . the incidence rates of ga - i vary between different races , and it has been reported as ~1/60,000 individuals in china ( 13 ) . to date , there are no reports of ga - i in uighur children . ga - i typically induces acute encephalopathic crisis within 3 to 36 months of delivery , due to non - specific factors , such as infection , fever and vaccinations . these typically result in induced striatal neuron degeneration , and often result in severe neurological sequela , such as dystonia and extrapyramidal symptoms ( 14 ) . an early diagnosis , together with a reasonable diet , energy supplements and active treatment towards complicating diseases ( such as induced acute encephalopathy ) could significantly improve the prognosis ; however , nearly one - third of pediatric patients experiencing ga - i suffer from severe neurological sequela even after aggressive treatment ( 15 ) . patients with incubative disease would exhibit no acute encephalopathic crisis , but would experience gradually progressive nervous system damage ( 16 ) . currently , pathogenesis study of ga - i typically focusses on the selective accumulation mechanisms of ga , other metabolites in the brain , and the neurotoxic mechanisms of ga and other metabolites ( 17 ) . the abnormal increasing of ga , 3-hydroxyglutaric acid and other metabolites in the brain might cause striatal neuronal degeneration , wide white matter degeneration and gliosis . the abnormal accumulation of metabolites would cause excitatory damage , energy metabolism damage and oxidative stress . in addition , other risk factors , such as glial activation , vascular injury , inflammatory factors and other causative factors , are involved in collaborative neurotoxic damage ( 18 ) . in the present study , case 1 exhibited neurological symptoms during treatment , with an onset age of 12 years . the patient lacked specific clinical symptoms , and lesions were only identified after completing a brain mri . following the mri , the patient 's family members were recommended for blood acylcarnitine and urine organic acid analysis . the results showed that the patient 's sister ( case 2 ) also had late - onset ga - i , but experienced no clinical symptoms or signs . macrocephaly is a typical characteristic of ga - i ( 14 ) , but this characteristic did not appear in either cases 1 or 2 . early onset ga - i commonly exhibits hypoevolutism or reverse development , muscle tonus disorder and seizure , and nearly half of patients exhibit acute neurological degeneration when under stress ( 19 ) . the symptoms of late - onset ga - i are relatively mild , with primary clinical manifestations of motion retrogression and paroxysmal headache , which typically develop premorbidly . patients usually have a relatively good prognosis and fast recovery , and their intelligence and motion abilities can resume to normal , suggesting that the age of onset is associated with clinical prognosis ( 20 ) . in the present study , case 1 exhibited headache with normal cognitive functions , and cranial mri exhibited focal patchy t2 flair high signals in the semi - oval area , corner and anteroposterior horns of te lateral ventricle . the clinical symptoms disappeared after treatment , while cranial mri exhibited no significant changes , consistent with previously reported literature ( 21,22 ) . achieving a clinical diagnosis of ga - i is difficult , and urine organic acid analysis is the key technology in screening and diagnosing ga - i . however , diagnostic screening could rely on gc / ms technology to analyze the levels of urine glutaric acid and 3-hydroxy - glutaric acid and ms / ms technology could be used to analyze the level of acetylcarnitine in blood . in addition , gcdh activity detection or gene testing can be used to diagnose ga - i ( 23,24 ) . in the present study , the two cases were confirmed because of the markedly increased concentrations of urine glutaric acid and 3-hydroxy - glutaric acid . the results from these two patients showed that glutaryl carnitine was increased , while free carnitine was reduced ; therefore , it is recommended the suspected ga - i patients should undergo urine organic acid analysis , the blood acylcarnitine ester spectrum should be monitored in order to confirm diagnosis . gcdh is a key enzyme in the catabolic pathways of tryptophan , lysine and hydroxylysine , and can catalyze the oxidative decarboxylation of glutaryl coenzyme a , generate crotonyl coenzyme a and co2 ; the gene for this enzyme was located at 19p13.2 , which is associated with > 200 types of pathogenic mutations ( 12 ) . different mutations result in different degrees of enzyme deficiency , and the residual enzyme activity is associated with a patient 's biochemical phenotype ( urinary ga content ) , but is not associated with clinical phenotype ( 12 ) . the analysis of gcdh mutation could further confirm the disease , thus guiding the genetic counseling of patients ' family members and the prenatal diagnosis of the next child . there may exist differences of gcdh hotspot mutations among ga - i patients in different races and regions . in caucasians , c. 1204c > t was the most common hotspot mutation ( 9 ) , while c. 914c > t was common in japanese patients ( 10 ) . the present study diagnosed two patients with ga - i on a genetic level in uighur , mainland of china , for the first time . both patients expressed the c. 1204c > t missense mutation , and the detection of the gcdh gene mutation in their parents revealed that both parents were carriers of the disease - causing gene , which further suggests that this disease shows features of a typical autosomal recessive inheritance disorder . the two patients in this study had blood connections , c. 532 g > a mutation ( from the mother ) and c. 1204c > t mutation ( from the father ) ; c. 532 g > a has not , to date , been reported in the chinese population before . because the two patients with late - onset ga - i were uighurs , and late - onset cases are easily misdiagnosed clinically , a question arises as to whether c. 532 g > a was the mutation hotspot of late - onset ga - i . or , whether the mutation is a hotspot in uighur individuals ; this remains to be investigated in large - sample studies . internationally , there are standardized treatments applied to ga - i disease ( 25 ) . however , the number of diagnosed cases in china is few , and popular treatments include a limiting protein diet ( particularly lysine and tryptophan ) , and supplementation with l - carnitine 100 mg/(kgday ) and vitamin b2 ( 200300 mg / day ) . during the treatment of cases 1 and 2 in this study , it was observed that the application of the above drugs needed to be gradually increased . during the dose - increasing process , particular attention should be paid towards pediatric patients to ensure that they can tolerate the doses . regarding the application of vitamin b2 , the reported method was much more recommended , namely 10 mg/(kgday ) ( 26 ) . the age of onset , treatment and diet of patients are closely associated with the prognosis of ga - i ( 27 ) . by performing gc - ms in newborns and high - risk screenings , an increasing number of patients with ga - i could obtain diagnosis in asymptomatic or early stages , so that early treatment can improve their prognosis ( 15 ) . a region in usa applied gs - ms technology to screen high - risk infants of an amish family between 1988 and 1994 , and several asymptomatic patients were identified ( 26 ) . early preventive treatment in these cases ensured that the patients did not experience neurological symptoms . however , ~78% of patients are not clearly diagnosed until striatal necrosis appears , which typically results in poor prognosis and disability ( 26 ) . poor prognosis may be associated with diarrhea , intermittent withdrawal of l - carnitine and vitamin b2 , diet or improper care . long term , standard treatment could reduce the occurrence of acute encephalopathy and dyskinesia , while discontinuing the treatment could result in irreversible neurological damage . the above conclusions indicate that ga - i may be associated with phenylketonuria , which can be easily treated . however , since the incidence of ga - i is markedly lower than phenylketonuria , large studies and screening would be difficult in china at this stage . however , once pediatricians are able to recognize specific clinical manifestations of ga - i , early relevant examinations and treatments can be applied . uighur account for > 50% of the total population in xinjiang , where ms / ms and gc / ms detection has only been performed in the past three years , due to limitations of the economy and cultural background . therefore , patients with clinical manifestations , such as macrocephaly , infection , dehydration or developmental regression after seizure , cranial mri showing bilateral temporal lobe arachnoid cyst , abnormal basal ganglia signals , and non - trauma and intracranial infection - related subdural effusion or blood , should be assessed for ga - i , since the early detection of this disease will result in early treatment and an improved prognosis . including ga - i into newborn screening programs would be an effective method for the early diagnosis of glutaric aciduria , although early treatment may not completely avoid damage to the nervous system , it could reduce neurological complications and save a lot of medical expenses ( 13 ) .
the aim of the present study was to investigate the clinical , biochemical and genetic mutation characteristics of two cases of late - onset glutaric aciduria type i ( ga - i ) in uighur . the clinical data and glutaryl - coa dehydrogenase ( gcdh ) genetic test results of two cases of late - onset ga - i in uighur were collected and analyzed , and reviewed with relevant literature . 
 one patient with late - onset ga - i primarily exhibited clinical intermittent headache , while the other patient was asymptomatic . 
 the urinary organic acid analysis detected a large number of glutaric acid and 3-hydroxy glutaric acid , 3-hydroxy - propionic acid . 
 one patient exhibited white matter degeneration in cranial magnetic resonance imaging ( mri ) and the other patient showed no abnormality . 
 the two patients both exhibited c. 1204c > t , p.r402w , heterozygous mutation , and c. 532 g > a , p.g178r , heterozygous mutation . 
 besides central nervous system infectious diseases , patients with clinical headache , cranial mri - suggested bilateral temporal lobe arachnoid cyst and abnormal signals in the basal ganglia should be highly suspected as late - onset ga - i . 
 early diagnosis and correct treatment are key to improve its prognosis .