Cases Of Maple Syrup Urine Disease Research Articles

The oral phenotype and dental management in patients with maple syrup urine disease; case report and scoping review

Background and objectivesThe literature about oral manifestations and dental management in maple syrup urine disease (MSUD) is sparse. The aim of this report is to present a new case of MSUD with special emphasis on oral findings and to review the relevant literature.MethodA case report of a 4-year-old boy with MSUD was described according to the CARE guidelines for describing case reports. Scoping review of relevant literature was performed, according to the PRISMA-ScR guidelines, by searching PubMed, Medline, Embase, and the grey literature for articles describing dental management and/or oral manifestations in MSUD.ResultsThe initial search identified 219 articles, but only 4 met the inclusion criteria. Rampant caries and plaque induced gingivitis were the main oro-dental findings in MSUD. Other oral findings included enamel hypoplasia, skeletal abnormalities, and abnormal oral behaviors. Disease-related factors appeared to play a major role in the development of the observed oral phenotype.ConclusionOral health in MSUD seems to be influenced by the reliance on semi-synthetic diet and associated neurocognitive complications. Tailored oral health promotional interventions should be included in the multidisciplinary management of patients with MSUD.

Genetic analysis by targeted next-generation sequencing and novel variation identification of maple syrup urine disease in Chinese Han population

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder that affects the degradation of branched chain amino acids (BCAAs). Only a few cases of MSUD have been documented in Mainland China. In this report, 8 patients (4 females and 4 males) with MSUD from 8 unrelated Chinese Han families were diagnosed at the age of 6 days to 4 months. All the coding regions and exon/intron boundaries of BCKDHA, BCDKHB, DBT and DLD genes were analyzed by targeted NGS in the 8 MSUD pedigrees. Targeted NGS revealed 2 pedigrees with MSUD Ia, 5 pedigrees with Ib, 1 pedigree with MSUD II. Totally, 13 variants were detected, including 2 variants (p.Ala216Val and p.Gly281Arg) in BCKDHA gene, 10 variants (p.Gly95Ala, p.Ser171Pro, p.Phe175Leu, p.Arg183Trp, p.Lys222Thr, p.Arg285Ter, p.Arg111Ter, p.S184Pfs*46, p.Arg170Cys, p.I160Ffs*25) in BCKDHB gene, 1 variant (p.Arg431Ter) in DBT gene. In addition, 4 previously unidentified variants (p.Gly281Arg in BCKDHA gene, p.Ser171Pro, p.Gly95Ala and p.Lys222Thr in BCKDHB gene) were identified. NGS plus Sanger sequencing detection is effective and accurate for gene diagnosis. Computational structural modeling indicated that these novel variations probably affect structural stability and considered as likely pathogenic variants.

Maple syrup urine disease: magnetic resonance imaging findings in three patients.

Maple syrup urine disease (MSUD) is an autosomal recessive inherited metabolic disorder, caused by branched-chain alpha-ketoacid dehydrogenase (BCKD) deficiency, leading to toxic accumulation of branched-chain amino acids (BCAAs) including leucine, isoleucine and valine and their corresponding a-ketoacids. The diagnosis of MSUD is based on elevated BCAAs and allo-isoleucine in plasma, and branched-chain hydroxyacids and ketoacids in urine. The identification of alloisoleucine >5 µmol/L is considered pathognomonic. Moreover, brain magnetic resonance imaging (MRI) showing atypical signal intensity and oedema is characteristic of MSUD. Recognition of the classical neuro-radiological findings of MSUD is particularly useful in local settings as many healthcare facilities lack the resources to measure Plasma Amino Acids (PAA). We report three cases of MSUD, in whom the disorder was strongly suspected at presentation, based on classical brain MRI findings, which was urgently confirmed by PAA analysis.

Congenital adrenal hyperplasia with maple syrup urine disease: An example of consanguinity impact.

Background: Maple syrup urine disease (MSUD) is a rare autosomal recessive metabolically inherited disorder, caused by an abnormal function of the branched-chain α-keto acid dehydrogenase complex in the mitochondria. Case Presentation: The proband was born after a full-term pregnancy and normal vaginal delivery, with a good Apgar score (8, 9 at 1 and 5 minutes) and the birth weight of 2.5 kg with ambiguous genitalia in the form of phallus-like structure (3 cm), the fusion of labio-scrotal folds and urogenital sinus. The third day after birth, the proband was lethargic and developed hyperkalemia and hyponatremia, which required intravenous fluid therapy and hormonal replacement with hydrocortisone and fludrocortisone. The treatment was based on the positive family history of congenital adrenal hyperplasia in an older male sibling. Laboratory tests, cytogenetic study, tandem mass spectroscopy, and surgery were performed for the affected individual (II-8) using standard procedures. The laboratory and the treatment revealed significant improvements. Follow-up tandem mass spectroscopy results were observed in the normal range. The affected individual was treated with prednisone (2.5 mg bid) and Florinef (Fludrocortisone) (0.1 mg OD). The subject had regular menses, while acne and hirsutism were not observed. Conclusion: We are reporting the first case of MSUD associated with CAH, 21-hydroxylase deficiency salt-losing type and suggest that glucocorticoids might have an important role in treating MSUD cases.

Selective Screening for Organic Acidurias and Amino Acidopathies in Pakistani Children.

To determine the frequency of organic acidurais (OA) and amino acidopathies (AA) in selected high-risk patients screened in two years. Retrospective Observational study. The Aga Khan University Hospital (AKUH), Karachi, from January 2013 to December 2014. Patients with OA and AA were included in the study and patients with IMDs other than OA and AA were excluded. Amino acids and organic acids were analyzed on high performance liquid chromatography and gas chromatography-mass spectrometry respectively. Clinical data and chromatograms of patients screened for IMDs were reviewed by chemical pathologist and metabolic physician. Eighty-eight cases (4.7%) were diagnosed including 41 OA (46.5%), 28 AA (31.8%) and 19 others (21.5%) from 1,866 specimens analyzed. Median age of the patients was 1.1 years, with high consanguinity rate (64.8%). Among OA, methyl CoA mutase deficiency was diagnosed in 9 (10.2%) and was suspected in 2 (2.3%) cases. Five (5.7%) cases of MHBD (2-methyl-3-hydroxybutyryl-CoA), 4 (4.5%) each of PPA (propionic aciduria) and HMG-CoA lyase deficiency, 3 (3.4%) cases each of IVA (isovaleric aciduria), multiple carboxylase deficiency, fructose-1, 6-biphosphatase deficiency, fumarase deficiency, GA-1 (glutaric aciduria type 1) and 2 (2.3%) cases of EMA (ethyl-malonic aciduria). AA included 8 (9.1%) cases of MSUD (maple syrup urine disease), 6 (6.8%) cases of CBS (cystathionine beta-synthetase) and UCDs (urea cycle disorders) each, 5 (5.7%) cases of hyperphenylalaninemia and 3 (3.4%) cases of hyperprolinemia were reported. Other inherited metabolic disorders included: 9 (10.2%) cases of intracellular cobalamin defects, 2 (2.3%) cases each of alkaptonuria, Canavan's disease, SUCL (succinate CoA ligase) deficiency, and 1 (1.1%) case each of DPD (dihydropyrimidine) deficiency, GA-2, NKH (non-ketotic hyperglycinemia), AADC (aromatic amino acid decarboxylase) deficiency. This study presents frequency of OA and AA in the high-risk Pakistani pediatric population analyzed locally.

Clinical outcome of major organic acidemias – A three years follow-up study

The term acidemia or (OA) applies to inborn errors of metabolism (IEM) in which organic acids accumulate in tissues and biological fluids. Classical organic acidurias include methylmalonic aciduria (MMA), propionic aciduria (PA), isovaleric aciduria (IVA) and maple syrup urine disease (MSUD). Aminoacidurias like phenylketonuria are common in the western population. Organic acidemias like MMA, PA and MSUD are more common in Asian countries, especially in India compared with the west. This study was conducted to determine the prevalence and treatment outcome of organic acidemias in a study population in India. Four hundred and twenty suspected cases of organic acidemias with an upper age limit of twelve years were enrolled over a two years period beteween January, 2007 and December, 2008, with a three years patient follow-up. Screening tests and thin layer chromatography followed by quantification of organic acids in urine and quantification of amino acids in blood by high performance liquid chromatography were done for detection of organic acidemias. Out of 420 patients, 45 patients (10.7%) were found to have organic acidemias, 15 cases of MMA, 16 cases of PA, 13 cases of MSUD, and one case of IVA were identified. Fifteen patients (33.3%) died during the course and remaining 30 are under therapeutic regimen and showed marked clinical improvement. Therapeutic regimens based on protein restriction, sodium bicarbonate (to correct acidosis), L-carnitine and vitamins were given to the patients. Prompt diagnosis helped to provide specific treatment to majority of these patients with rapid improvement in symptomatology.

Eleven novel mutations of the BCKDHA, BCKDHB and DBT genes associated with maple syrup urine disease in the Chinese population: Report on eight cases

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder that affects the degradation of branched chain amino acids (BCAAs). Only a few cases of MSUD have been documented in Mainland China, and prenatal diagnosis has not been performed so far. In this report, 8 patients (4 girls and 4 boys) with MSUD from 8 unrelated Chinese families were diagnosed at the age of 9 days to 1 year and 8 months. The diagnosis was confirmed by serum BCAAs and genetic analyses. Among the 8 patients, only one was detected by newborn screening. The remaining 7 patients were admitted because of neurological disorders and underwent selective screening. Significantly elevated BCAAs were observed in 7 patients. One patient was diagnosed by post-mortem study. 12 mutations were found in the BCKDHA, BCKDHB and DBT genes. 11 of these mutations were novel: c.178G > T, c.491T > C, c.740A > G, c.1214_1219dupCCAACC and IVS6+1delG in BCKDHA; c.482T > G, c.508C > T, c.767A > G, c.768C > G and IVS4,−2A > C in BCKDHB; and c.1A > G in DBT. Only one mutation, c.659C > T in the BCKDHA gene, had been previously reported. 7 patients were treated by dietary intervention and symptomatic therapy. 6 of them showed clinical improvement. The mother of one patient who died from MSUD underwent amniocentesis during her second pregnancy. The BCAAs level in her amniotic fluid was normal. Only one heterozygous mutation, IVS4,−2A > C in the BCKDHB gene, was detected in the cultured amniocytes. The results revealed that the fetus was not affected by MSUD. Normal development and the blood BCAAs profile confirmed the prenatal diagnosis after birth. Thus, we identified eleven novel mutations associated with MSUD in the Chinese population. Prenatal diagnosis of MSUD was successfully performed on one fetus by genetic analysis of the cultured amniocytes.

Different Gene Preferences of Maple Syrup Urine Disease in the Aboriginal Tribes of Taiwan

Maple syrup urine disease (MSUD) is a rare inborn error of metabolism caused by a deficiency of the branched-chain α-ketoacid dehydrogenase (BCKD) complex. Mutations in any one of the three different genes encoding for the BCKD components, namely, BCKDHA, BCKDHB, and DBT, may be responsible for this disease. In Taiwan, few MSUD cases were diagnosed clinically, and most of these patients are from Aboriginal tribes. To identify and detect the carrier frequency of MSUD in Taiwanese Aboriginal tribes, we performed biochemical and molecular studies from peripheral blood in MSUD patients and dried blood on filter paper in the enrolled screened populations. Homozygous A208T and I281T of BCKDHA were found in two patients from Hans (non-Aboriginal Taiwanese), respectively; compound heterozygous mutations of the DBT gene [4.7kb deletion/c.650-651insT (L217F or L217fsX223) and c.650-651insT/c.88-89delAT] were found in two patients from Amis, respectively, after direct DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism studies. There were no cases of deleted 4.7-kb heterozygote out of 302 normal people (Hans, n=125; Atayal, n=156; and Saisiyat, n=21); by contrast, the DBT mutations c.650-651insT and deleted 4.7-kb heterozygote were noted in 2/121 and 1/121, respectively, from the general population of the Amis, a southeastern Taiwanese tribe. Although the Taiwanese Austronesian Aboriginal tribes are considered to share a common origin, different gene preferences of MSUD were noted. The novel DBT mutation c.650-651insT was more prevalent than the deleted 4.7-kb heterozygote in the Amis population. The reported 4.7-kb deletion indicating a possible founder mutation may be preserved in the southern and eastern, but not in northern Aboriginal tribes of Taiwan.

Maple Syrup Urine Disease (MSUD): A Case with Long-Term Follow-up after Liver Transplantation

Maple syrup urine disease (MSUD) is a rare hereditary metabolic condition where the body is unable to breakdown amino acids causing toxic buildup. Acute and long-term management of MSUD involves a restricted diet and regular monitoring of amino acid levels; however, more recently liver transplants have been shown to be successful in treating this condition. Even with successful management of MSUD there is evidence from pediatric cases that shows a distinct pattern of neurocognitive deficits associated with this condition, including impaired nonverbal skills and psychomotor functioning with relatively intact verbal abilities. In the present paper, we report an adult case of MSUD with associated neurocognitive deficits and functional limitations following liver transplantation. Neuroimaging revealed no structural abnormalities, while the results from the neuropsychological evaluation showed impairment in visual-spatial processing, attention, executive functioning, and psychomotor abilities, with relative strengths in verbal skills. The patient also showed reduced adaptive functioning and mild anxiety. This case demonstrates neurocognitive deficiencies within the context of normal magnetic resonance imaging. The possible underlying mechanism of this neuropsychological profile is discussed in relation to other neurodevelopmental models.

Diagnostic Tools of Early Brain Disturbances in an Asymptomatic Neonate with Maple Syrup Urine Disease

Maple syrup urine disease (MSUD) is a rare inherited metabolic disorder resulting from the defective activity of branched-chain 2-ketoacid dehydrogenase complex. Routine screening of newborn with tandem mass spectroscopy on the third day of life may detect elevated branched-chain amino acids in blood before the appearance of encephalopathic symptoms in MSUD cases. If undiagnosed by such a routine screening test, patients often present with encephalopathy and seizures. Clinical neurologic examination is supplemented by electroencephalography and imaging. Here, we report abnormal amplitude-integrated electroencephalography, electroencephalography, magnetic resonance imaging, and magnetic resonance imaging spectroscopy findings in a neurologically asymptomatic male newborn who was diagnosed with MSUD at the third week of life. These neurologic disturbances disappeared at the fourth month of life with appropriate special diet. Therefore, even in already asymptomatic cases, early neurologic deterioration of brain metabolism and structure can be detected with these early laboratory findings, indicating the importance of early diagnosis and management. Patients may also benefit from these investigations during the follow-up period.

Unusual Imaging Findings in Brain and Spinal Cord in Two Siblings With Maple Syrup Urine Disease

Maple syrup urine disease (MSUD) is a rare metabolic disease affecting the neural tissue. While the brain abnormalities present on MRI are well known, spinal imaging features have not been studied. We herewith report an unusual finding of enlarged Virchow Robin spaces in brain and novel spinal cord changes in two biochemically diagnosed cases of MSUD. To the best of our knowledge, spinal MRI findings in cases of MSUD have not been previously reported. Knowledge of spinal MRI findings may be useful in diagnosis of this rare disorder.

Diagnosis of major organic acidurias in children: two years experience at a tertiary care centre.

Organic acid disorders are inherited metabolic disorders in which organic acids accumulate in tissues and biological fluids of affected individuals. Classical organic acidurias include methylmalonic aciduria, propionic aciduria, isovaleric aciduria and maple syrup urine disease (MSUD). They are considered the most frequent metabolic disorders among severely ill children. Patients frequently present with acute symptoms early in life. 420 cases clinically suspected to have organic aciduria, with upper age limit of 12years for a 2-year period (January 2007-December 2008) were enrolled into this study. Metabolic acidosis and neurological symptoms were the most common signs. Screening tests and thin layer chromatography were done for detection of organic acidurias. Identification and quantitation of organic acids in urine and quantification of amino acids in blood were done by high performance liquid chromatography. Out of 420 patients, 45 patients (10.7%) were found to have organic acidurias. 15 cases of methylmalonic aciduria, 16 cases of propionic aciduria, 13 cases of MSUD, and one case of isovaleric aciduria were diagnosed. Results demonstrate the importance of testing for organic acidurias. Since organic aciduria may cause irreversible brain damage if not treated, we recommend selective screening amongst severely ill children despite implied extra costs.

Maple syrup urine disease: Further evidence that newborn screening may fail to identify variant forms

Newborn screening (NBS) by tandem mass spectrometry (MS/MS) has allowed for early detection and initiation of treatment in many patients with maple syrup urine disease (MSUD) (OMIM 248600), however, a recent report suggests that variants forms may be missed. Information on these patients is limited. We present clinical, biochemical and molecular information on patients with variant forms of MSUD not detected by the California Newborn Screening Program. Between July 2005 and July 2009, 2200,000 newborns were screened in California by MS/MS. Seventeen cases of MSUD were detected and three (two siblings) were missed. Additionally, the NBS cards of two siblings with late onset MSUD, who were born pre-expanded NBS, were retrospectively analyzed. None of the five patients met criteria to be considered presumptive positive for MSUD (leucine>200micromol/L and a ratio of leucine/alanine>or=1.5). Alloisoleucine (allo-ile) was subsequently analyzed in the NBS cards of all five patients, two of whom were found to have elevated levels. The proband in each family was diagnosed following symptoms triggered by an intercurrent illness or increased protein intake. At diagnosis, leucine levels ranged between 561 and >4528micromol/L, and allo-ile ranged from 137 to 239micromol/L. Two affected siblings had normal plasma amino acids when asymptomatic; however, their biochemical profiles were diagnostic of MSUD during intercurrent illnesses. The median age at diagnosis of all patients was one year (range 0.8-6.7). Heterozygous BCKDHB (E1beta) mutations (c.832G>A/c.970C>T) were identified in one family and a homozygous DBT (E2) sequence variant (c.1430 T>G) in another. The third family had one identifiable DBT mutation (c.827T>G), however, a second mutation was not detected. This report provides further evidence that NBS by MS/MS is unable to detect all cases of MSUD. Second-tier testing with allo-ile may improve sensitivity; however, some children with variant forms will invariably be missed.

Utilization of Blood Spot Testing for Metabolic-Genetic Disorders in Honduras: Is it Time for Newborn Screening?

Honduran infant mortality (20/1000) has fallen below the Latin American newborn screening target rate (<30/1000). The authors report 2 Honduran maple syrup urine disease cases and a newborn screening pilot study. The first infant, diagnosed by plasma/urine testing in the U.S., prompted this study. Although marked clinical/radiological improvement occurred after treatment, moderate neurodevelopmental delays persist at 5 years. This 1-month, prospective study used blood spot specimens from hospitalized term Honduran neonates shipped overnight to South Carolina for routine newborn screening with electronic result submission to Honduras for follow-up. Of 88 consecutive neonates (mean age: 4.2 days, standard deviation: 4.2 days) tested, 24 (0.6%) of 3837 completed tests were positive. Another infant with maple syrup urine disease, diagnosed after study completion by blood spot testing, later died. The study findings indicate that collaborative blood spot testing aids in the diagnosis of Honduran metabolic-genetic disease. Newborn screening is now needed to diagnose and treat these diseases before morbidity/mortality develops.

Acrodermatitis Enteropathica‐Like Eruption in Metabolic Disorders: Acrodermatitis Dysmetabolica Is Proposed as a Better Term

Acrodermatitis acidemica is a recently proposed term for the rash that is similar to acrodermatitis enteropathica, which is encountered in organic acidemias. However, acrodermatitis enteropathica-like eruption may be seen in metabolic disorders other than organic acidemias. The aim of this study was to evaluate the clinical features of acrodermatitis enteropathica-like eruption secondary to metabolic disorders. Clinical and demographic features of 12 patients with acrodermatitis enteropathica-like eruption were prospectively evaluated between 2004 and 2006 in this single-center study. Among the 12 patients, underlying metabolic disorders included maple syrup urine disease (n = 5), methylmalonic acidemia (n = 3), phenylketonuria (n = 2), ornithine transcarbamylase deficiency (n = 1), and propionic acidemia (n = 1). Mean age at first presentation was 29.9 months. Mean duration of acrodermatitis enteropathica-like eruption at the time of presentation was 25.2 days. The diaper area was involved in all presentations. Plasma zinc level was measured in 62.5% (n = 10) of the presentations and all had normal levels. All phenylketonuria cases had a low plasma phenylalanine level, and a low plasma isoleucine level was observed in the propionic acidemia case and all maple syrup urine disease cases. The rash responded dramatically to appropriate diet management in all cases. In this study, acrodermatitis enteropathica-like eruption was noted in various metabolic disorders, including organic acidemias. We suggest that acrodermatitis dysmetabolica might be a better term for acrodermatitis enteropathica-like eruption occurring secondary to metabolic disorders other than acquired zinc deficiency.

Avances en el diagnóstico y tratamiento de la enfermedad de jarabe de arce, experiencia en Galicia

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder caused by an inherited deficiency of branched chain alpha-ketoacid dehydrogenase activity. Accumulation of the amino acids leucine, isoleucine, valine and alloisoleucine and their metabolic products in cells and biological fluids results in severe brain dysfunction. We present three cases of MSUD diagnosed in Galicia since 2000, the year in which the Extended Newborn Screening Program by tandem mass spectrometry was started in this region. One of the patients was diagnosed on the basis of early clinical presentation and the others by neonatal screening. Enzymatic and molecular studies confirmed two classic cases of MSUD and an intermediate variant. We describe the clinical and biochemical details at confirmation of diagnosis and the long-term outcome of the three patients. Throughout follow-up, all the patients maintained adequate leucine levels, which were near the normal range (mean levels: 220, 177 and 252 micromol/L, respectively). Several moderate metabolic decompensations were observed but leucine levels only occasionally exceeded 1000 micromol/L (one day in two patients). IQ tests were performed in all patients and scores were within the normal range. In view of our results, we believe the following measures are essential to improve the prognosis of MSUD: inclusion of this disease in Expanded Neonatal Screening Programs with early samples (at 2-3 days of life); aggressive treatment in the initial phase and during acute decompensations; strict metabolic control to prevent crises, monitoring of branched-chain amino acids (dried blood spot sample), and maintenance of long term plasma leucine levels below 300 micromol/L.

A novel deletion creating a new terminal exon of the dihydrolipoyl transacylase gene is a founder mutation of Filipino maple syrup urine disease

Maple syrup urine disease (MSUD) is a rare, autosomal-recessive disorder of branched-chain amino-acid metabolism. In the Philippines, many MSUD cases have been diagnosed clinically. Here, molecular analysis of the dihydrolipoyl transacylase (E2) gene was done in 13 unrelated families from the Philippines. A novel deletion spanning 4.1 kb of intron 10 and 601 bp of exon 11, caused by non-homologous recombination between an L1 repeat in intron 10 and an Alu repeat in exon 11, was found in 8 out of 13 families, with 5 of them being homozygous for the mutation, implicating it as a founder mutation of Filipino MSUD. The resulting mutant E2 mRNA contains a 239-bp insertion after exon 10, thereby producing a new terminal exon. Large-scale population screening of the deletion revealed that one carrier of the mutation was identified in 100 normal Filipinos. These findings suggest that a limited number of mutations might underlie MSUD in the Filipino population, potentially facilitating prenatal diagnosis and carrier detection of MSUD in this group.

Maple syrup urine disease. Complete defect of the E1 beta subunit of the branched chain alpha-ketoacid dehydrogenase complex due to a deletion of an 11-bp repeat sequence which encodes a mitochondrial targeting leader peptide in a family with the disease.

Branched chain alpha-ketoacid dehydrogenase (BCKDH) deficiency results in maple syrup urine disease (MSUD). We examined the molecular basis of familial cases of MSUD by analyzing the activity, subunit structure, mRNA sequence, and genome structure of the affected enzyme. The BCKDH activity in the proband with MSUD was approximately 6% of the normal control level. Immunoblot analysis revealed that the E1 beta subunit of BCKDH was absent and that the E1 alpha subunit of BCKDH was markedly reduced. We amplified the cDNAs of the E1 alpha subunit and the E1 beta subunit of the BCKDH complex obtained from cells of the patient, using the polymerase chain reaction method, then sequenced the amplified cDNAs. The deduced amino acid sequence for the E1 alpha subunit of the patient's cell was normal. An 11-bp deletion was identified in the region that encoded the mitochondrial targeting leader peptide in the E1 beta cDNA. This 11-bp sequence is found in the first exon of the BCKDH-E1 beta gene, as a direct tandem repeat. Amplification of genomic DNA revealed that the consanguineous parents were heterozygous for this mutant allele, and sister and brother of the patient with the disease were homozygous for this mutant allele. This 11-bp deletion mutation caused a change in the reading frame and the mature E1 beta protein was defective. These observations show the biological importance of the E1 beta subunit of BCKDH to maintain normal function of the enzyme activity. The absence of the E1 beta subunit results in instability of the E1 alpha subunit.

The diagnosis and management of MSUD in Saudi Arabia by using two different methods

Plasma amino acid concentrations were measured in Maple Syrup Urine Disease (MSUD) infants using reversed phase high performance liquid chromatography (HPLC). The technique involved an automated data acquisition system and phenylisothiocyanate (PITC) pre-column derivatization. During a period of three years more than 14 cases of MSUD have been confirmed in our hospital suggesting an alarmingly high rate of incidence of this disease in the Kingdom as compared to the West. We present here a simple and reliable method of quantitating the branched chain and other amino acid concentrations in plasma samples of children with metabolic disorders. In addition, we also present a fluorimetric COBAS based enzymatic method for the rapid semiquantitative measurement of branched chain amino acids for a disease in which a prompt initial diagnosis is essential.

Evidence for both a regulatory mutation and a structural mutation in a family with maple syrup urine disease.

Maple syrup urine disease (MSUD) results from a deficiency of branched chain alpha-ketoacid dehydrogenase (BCKDH). We have studied the etiology of MSUD by determining the enzyme activity, protein, and mRNA levels of BCKDH in fibroblasts from a classic MSUD patient and his parents. By enzymatic amplification of the patient's mRNA followed by cloning and DNA sequencing, we have identified a T to A transversion that alters a tyrosine to an asparagine at residue 394 of the E1 alpha subunit. Amplification of both mRNA and genomic DNA, in combination with allele-specific oligonucleotide hybridization, demonstrated that the father was heterozygous for this mutant allele. The mother was homozygous for the allele encoding the normal Tyr394, but expressed only about half of the normal level of mRNA and protein. The patient was genetically heterozygous for this altered allele, although only the abnormal allele was expressed as mRNA. We conclude that the patient was a compound heterozygote, inheriting an allele encoding an abnormal E1 alpha from the father, and an allele from the mother containing a cis-acting defect in regulation which abolished the expression of one of the E1 alpha alleles. Our results revealed for the first time that a case of MSUD was caused by structural and regulatory mutations involving the E1 alpha subunit.