Hypoglycaemia and elevated urine ethylmalonic acid in a child homozygous for the short-chain acyl-CoA dehydrogenase 625G > A gene variation

The aim of this case report is to call attention to short-chain acyl-CoA dehydrogenase (SCAD) deficiency as a possible contributory factor to hypoglycaemia in childhood. We report on a previously healthy 14 mo-old Danish boy who presented with hypoglycaemia and metabolic acidosis after a few days of upper airway infection. After two days on a normal diet, he recovered clinically and biochemically. A thorough biochemical examination did not reveal the cause of the hypoglycaemia. However, the excretion of ethylmalonic acid in two morning urine samples was moderately increased, and hence the SCAD gene was screened for mutations. We found the child homozygous for the G > A SCAD gene variation at position 625. Conclusion: In this patient, reduced function of the SCAD protein is reflected in the excretion of ethylmalonic acid, a marker of intracellular accumulation of butyryl-CoA and the cytotoxic butyric acid. Furthermore, gluconeogenesis might be compromised owing to lack of reducing equivalents from the oxidation of short-chain fatty acids in the fasting or stressed state, thus contributing to the predisposition for fasting hypoglycaemia.     

Short-chain acyl-coenzyme A dehydrogenase deficiency in mice

A murine model for short-chain acyl-coenzyme A dehydrogenase (SCAD) deficiency has been identified and characterized in BALB/cByJ mice. These mice have undetectable SCAD activity, severe organic aciduria; excreting ethylmalonic and methylsuccinic acids and N-butyrylglycine, and develop a fatty liver upon fasting or dietary fat challenge. The mutant mice develop hypoglycemia after an 18-h fast, and have elevated urinary and muscle butyrylcarnitine concentrations. Most of these findings parallel those of human disorders associated with SCAD deficiency and other beta-oxidation defects. This mouse model presents important opportunities to investigate the biology of mammalian fatty acid metabolism and the related human diseases.     

Rare disorders of metabolism with elevated butyryl- and isobutyryl-carnitine detected by tandem mass spectrometry newborn screening

Tandem mass spectrometry was adopted for newborn screening by North Carolina in April 1999. Since then, three infants with short-chain acyl-CoA dehydrogenase (SCAD) and one with isobutyryl-CoA dehydrogenase deficiency were detected on the basis of elevated butyrylcarnitine/isobutyrylcarnitine (C4-carnitine) concentrations in newborn blood spots analyzed by tandem mass spectrometry. For three SCAD-deficient infants, biochemical evaluation included a plasma acylcarnitine profile with markedly elevated C4-carnitine, urine organic acid analysis with markedly elevated ethylmalonic and 2-methylsuccinic acids, and markedly elevated [U-13C]butyrylcarnitine concentrations in medium from fibroblasts incubated with [U-13C]palmitic acid and excess l-carnitine, consistent with classic SCAD deficiency. Two of three infants diagnosed with classic SCAD deficiency remained asymptomatic; however, the third infant presented with seizures and a cerebral infarct at 10 wk of age. All three infants had putatively inactivating mutations in both alleles of the SCAD gene. The highly elevated plasma C4-carnitine levels in the three infants detected by newborn screening tandem mass spectrometry differentiated them from infants and children who were homozygous or compound heterozygous for one of two SCAD gene susceptibility variations; for the latter group the C4-carnitine levels were normal. Isobutyryl-CoA dehydrogenase deficiency in a fourth infant was confirmed after isolated elevation of C4-carnitine in the acylcarnitine profile.     

Prevalent mutations in fatty acid oxidation disorders: diagnostic considerations

The mutational spectrum in a given disease-associated gene is often comprised of a large number of different mutations, of which a single or a few are present in a large proportion of diseased individuals. Such prevalent mutations are known in four genes of the fatty acid oxidation: the medium-chain acyl-CoA dehydrogenase (MCAD) gene; the short-chain acyl-CoA dehydrogenase (SCAD) gene; the long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) gene and the carnitine-palmitoyl-CoA transferase II (CPT II) gene. In MCAD deficiency the analysis confirms the conventional wisdom that individuals carrying the prevalent 985A>G mutation are at risk of developing life-threatening attacks. In SCAD/ethylmalonic aciduria, on the other hand, the presence of the prevalent susceptibility variations, 625A and 511T, in the SCAD gene seems to require additional genetic and cellular factors to be present in order to result in a phenotype. For the prevalent mutations in the LCHAD and CPT II genes further data are needed to evaluate the penetrance and risk of manifest disease when carrying these mutations. Conclusion Assessment of the prevalence of a prevalent mutation in the mutation spectrum of the disease in question and determination of the carrier frequency in the general population may help in elucidating the penetrance of the genotype. This is exemplified in disorders of mitochondrial fatty acid oxidation.     

Approach to management of malignant hyperthermia-like syndrome in pediatric diabetes mellitus.

BACKGROUND: Hyperglycemic hyperosmolar nonketotic syndrome (HHNS) is usually associated with type 2 diabetes mellitus and is rare in children. However, a fatal malignant hyperthermia-like syndrome (MHLS) with rhabdomyolysis associated with new-onset diabetes mellitus and HHNS in adolescents has been described. DESIGN/METHODS: Case series. RESULTS: A 16-yr-old obese male (case A) and a 10-yr-old mid-pubertal nonobese female (case B) presented within a 6-month period with emesis, altered mental status, blood glucose >1600 mg/dL, and laboratory evidence of rhabdomyolysis. Case A developed fever after initiation of insulin therapy, along with refractory hypotension and multiorgan failure. He died 14 hrs after admission. Case B developed fever before insulin therapy, was treated with dantrolene, and made a full recovery. Metabolic workup showed evidence of short-chain acyl-CoA dehydrogenase (SCAD) deficiency. CONCLUSIONS: We report two cases of malignant hyperthermia-like syndrome associated with HHNS in adolescents. Their respective fluid management and clinical courses are described. Dantrolene therapy should be initiated immediately after this syndrome is recognized. We believe it is unlikely insulin is the sole trigger for MHLS. Case B is unique in that there was evidence of SCAD deficiency, a metabolic defect that we propose could lead to MHLS. We recommend that all patients with HHNS and MHLS be evaluated for an underlying metabolic disorder.     

Fructose-1,6-diphosphatase deficiency: glycerol excretion during fasting test

A Turkish boy had suffered since the age of 10 months from recurrent attacks of severe metabolic acidosis and hypoglycaemia precipitated by moderate respiratory tract infections. A liver biopsy showed lack of fructose 1,6-diphosphatase and absence of phosphorylase. The patient died in shock following fructose ingestion. Upon fasting, acidosis with increased lactate and glycerol excretion was found. Findings indicate that, in this inherited disorder of gluconeogenesis, lactic acidosis combined with increased glycerol excretion upon fasting are of diagnostic importance.     

Role of common gene variations in the molecular pathogenesis of short-chain acyl-CoA dehydrogenase deficiency

ABSTRACT Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is considered a rare inherited mitochondrial fatty acid oxidation disorder. Less than 10 patients have been reported, diagnosed on the basis of ethylmalonic aciduria and low SCAD activity in cultured fibroblast. However, mild ethylmalonic aciduria, a biochemical marker of functional SCAD deficiency in vivo, is a common finding in patients suspected of having metabolic disorders. Based on previous observations, we have proposed that ethylmalonic aciduria in a small proportion of cases is caused by pathogenic SCAD gene mutations, and SCAD deficiency can be demonstrated in fibroblasts. Another - much more frequent - group of patients with mild ethylmalonic aciduria has functional SCAD deficiency due to the presence of susceptibility SCAD gene variations, i.e. 625G>A and 511C>T, in whom a variable or moderately reduced SCAD activity in fibroblasts may still be clinically relevant. To substantiate this notion we performed sequence analysis of the SCAD gene in 10 patients with ethylmalonic aciduria and diagnosed with SCAD deficiency in fibroblasts. Surprisingly, only one of the 10 patients carried pathogenic mutations in both alleles, while five were double heterozygotes for a pathogenic mutation in one allele and the 625G>A susceptibility variation in the other. The remaining four patients carried only either the 511C>T or the 625G>A variations in each allele. Our findings document that patients carrying these SCAD gene variations may develop clinically relevant SCAD deficiency, and that patients with even mild ethylmalonic aciduria should be tested for these variations.     

Growth hormone release during insulin tolerance test on children of short stature

The HGH response to insulin-induced hypoglycaemia has been studied in 31 children with short stature. Ten patients have been classified as hypopituitary dwarfs, and all these patents showed an HGH increment of less than 10 ng/ml from fasting levels. In six of these there were signs of deficiency of other pituitary hormones and two had a craniopharyngioma. In fifteen children the diagnosis was premordial dwarfism or constitutional delay in growth. Two patients in this group showed a subnormal HGH response to insulin-induced hypoglycaemia. In five patients with Turner's syndrome and in two patients with chondrodystrophy the HGH response was normal when compared to a control group. Other parameters compared were the blood glucose levels during the insulin-induced hypoglycaemia, PBI, excretion of 17-OH corticosteroids after metyrapone, urinary gonadotropins and the bone age. The difficulties in the interpretation of different tests are discussed and some other possible tests for the study of HGH release have been described. On the basis of this study measurements of HGH levels during insulin-induced hypoglycaemia is a useful aid in the diagnosis of hypopituitarism. When borderline results are found further tests or short term therapy with HGH is necessary.     

Hepatic glycogen synthetase deficiency. Definition of syndrome from metabolic and enzyme studies on a 9-year-old girl.

In the 13 years since hepatic glycogen synthetase deficiency was first described in identical twins no further cases seem to have been observed. We report a child who had suffered from occasional morning convulsions since the age of 7. Three 24-hour metabolic profiles showed fasting hypoglycaemia, hyperketonaemia, but normal lactate. Hyperglycaemia and hyperlactataemia occurred after meals. Glucagon caused a rise in glucose 3 hours after a meal with a fall in lactate and alanine; no effect of glucagon was seen after a 12-hour fast. Normal increments in glucose followed oral galactose or alanine. Liver and abdominal wall muscle biopsies were taken. Glycogen content was subnormal in liver but normal in muscle. Glycogen synthetase (EC 2.4.1.11) was virtually absent from liver but fully active in muscle. Hepatic glycogen synthetase deficiency causing fasting hypoglycaemia has been confirmed. It is postulated that some children with "ketotic hypoglycaemia" may suffer from this disorder.     

Medium-chain acyl-CoA dehydrogenase deficiency in children with non-ketotic hypoglycemia and low carnitine levels

Three children in two families presented in early childhood with episodes of illness associated with fasting which resembled Reye's syndrome: coma, hypoglycemia, hyperammonemia, and fatty liver. One child died with cerebral edema during an episode. Clinical studies revealed an absence of ketosis on fasting (plasma beta-hydroxybutyrate less than 0.4 mmole/liter) despite elevated levels of free fatty acids (2.6-4.2 mmole/liter) which suggested that hepatic fatty acid oxidation was impaired. Urinary dicarboxylic acids were elevated during illness or fasting. Total carnitine levels were low in plasma (18-25 mumole/liter), liver (200-500 nmole/g), and muscle (500-800 nmole/g); however, treatment with L-carnitine failed to correct the defect in ketogenesis. Studies on ketone production from fatty acid substrates by liver tissue in vitro showed normal rates from short-chain fatty acids, but very low rates from all medium and long-chain fatty acid substrates. These results suggested that the defect was in the mid-portion of the intramitochondrial beta-oxidation pathway at the medium-chain acyl-CoA dehydrogenase step. A new assay for the electron transfer flavoprotein-linked acyl-CoA dehydrogenases was used to test this hypothesis. This assay follows the decrease in electron transfer flavoprotein fluorescence as it is reduced by acyl-CoA-acyl-CoA dehydrogenase complex. Results with octanoyl-CoA as substrate indicated that patients had less than 2.5% normal activity of medium-chain acyl-CoA dehydrogenase. The activities of short-chain and isovaleryl acyl-CoA dehydrogenases were normal; the activity of long-chain acyl-CoA dehydrogenase was one-third normal. These results define a previously unrecognized inherited metabolic disorder of fatty acid oxidation due to deficiency of medium-chain acyl-CoA dehydrogenase.     

Quantitation of urinary carnitine esters in a patient with medium-chain acyl-coenzyme A dehydrogenase deficiency: effect of metabolic state and L-carnitine therapy

Urinary carnitine esters were quantitated in an infant with medium-chain acylcoenzyme A dehydrogenase deficiency by means of a highly sensitive and specific radioisotopic exchange high-pressure liquid chromatography method. During fasting, the excretion of free carnitine and of acetylcarnitine, octanoylcarnitine, and hexanoylcarnitine was increased. The fractional tubular reabsorption of free carnitine was decreased, suggesting a renal leak of free carnitine. In the symptom-free, fed state, only minor amounts of free carnitine and of short-chain acylcarnitine, octanoylcarnitine, and hexanoylcarnitine were present in urine, and carnitine loss occurred in the form of "other" carnitine esters not exceeding that of control subjects. During L-carnitine therapy, the excretion of free carnitine, short-chain acylcarnitine, octanoylcarnitine, and hexanoylcarnitine, and particularly of "other" carnitine esters, was increased, suggesting a possible detoxifying effect of administered carnitine that is not confined to the elimination of octanoic and hexanoic acids. The employed method detects very low urinary concentrations of octanoylcarnitine and hexanoylcarnitine (less than 1 mumol/L) characteristic of medium-chain acyl-coenzyme A dehydrogenase deficiency and may be useful in screening for this disease, which has been associated with sudden infant death.     

Short-chain acyl-coenzyme A dehydrogenase activity, antigen, and biosynthesis are absent in the BALB/cByJ mouse.

BALB/cByJ (J) mice have short-chain acyl-CoA dehydrogenase (SCAD) deficiency and an organic aciduria similar to that of human SCAD deficiency. [9,10(n)-3H]- and [15,16(n)-3H]palmitate oxidations in J mouse fibroblasts were 96 and 35% of control, respectively, consistent with an isolated SCAD defect. Acyl-CoA dehydrogenase activities were assayed in muscle and fibroblast mitochondria from BALB/cBy controls (Y) and SCAD-deficient J mice. Medium-chain acyl-CoA dehydrogenase (MCAD) activities were comparable in both J and Y mice from all tissues. In the presence of MCAD antiserum, SCAD activities in J mice were undetectable in both tissues. Apparent Km and Vmax values in liver mitochondria suggested a somewhat increased affinity of MCAD for butyryl-CoA in J mice, as compared with MCAD from other species. Immunoblot studies using mitochondria revealed identical apparent SCAD molecular weight in liver, muscle, and fibroblasts from Y mice and no detectable SCAD antigen in J mice; MCAD antigen was detected in comparable amounts from both Y and J mice. Radiolabeling and immunoprecipitation studies in J mouse fibroblasts revealed no SCAD synthesis, but normal MCAD synthesis. These data argue against the existence of tissue-specific SCAD isoforms in the mouse and confirm that this mouse strain is a model for the human organic aciduria resulting from this beta-oxidation defect.     

Ketotic (Idiopathic Glucagon Unresponsive) Hypoglycaemia: Diazoxide Effects*

Glucagon unresponsiveness in the fasting state characterizes a variety of hypoglycaemia with infrequent episodes usually occurring in the early morning with good health between attacks. Vomiting commonly accompanies the episodes. This variety of idiopathic hypoglycaemia has been called `ketotic hypoglycaemia'', but ketonuria may be an inconsistent finding. 13 patients were compared to 8 contrast subjects with other varieties of hypoglycaemia and to 7 children without hypoglycaemia to confirm the abnormality of response to glucagon in the fasting state. 9 children were studied before and after treatment with diazoxide, 15 mg/kg per day for 3 days. 6 subjects experienced restoration of fasting glucagon response with diazoxide. The difference between responding and nonresponding subjects could either be due to variability in expression of the same metabolic defect or represent different defects in fasting energy metabolism.     

Ketotic (Idiopathic Glucagon Unresponsive) Hypoglycaemia: Catecholamine Excretion and Effects of Ephedrine Therapy*

Two children with intermittent hypoglycaemia, associated with vomiting and occurring in the morning after breakfast, were unresponsive to the hyperglycaemic effect of glucagon in the fasting state. Fed-state glucagon response was normal. Urinary catecholamine excretion rate tripled during 18 to 24 hours of fasting. Treatment with ephedrine sulphate 2·5 mg/kg body weight per day divided into 6-hourly doses, much improved fasting tolerance and restored the glycaemic response to glucagon in the fasting state. The ephedrine was without side effects and has completely eradicated hypoglycaemic episodes in one of the children during 22 months use.     

Variations in IBD (ACAD8) in children with elevated C4-carnitine detected by tandem mass spectrometry newborn screening

The isobutyryl-CoA dehydrogenase (IBD) enzyme is involved in the degradation of valine. IBD deficiency was first reported in 1998 and subsequent genetic investigations identified acyl-CoA dehydrogenase (ACAD) 8, now IBD, as the gene responsible for IBD deficiency. Only three individuals homozygous or compound heterozygous for variations in the IBD gene have been reported. We present IBD deficiency in an additional four newborns with elevated C(4)-carnitine identified by tandem mass spectrometry (MS/MS) screening in Denmark and the United States. Three showed urinary excretions of isobutyryl-glycine, and in vitro probe analysis of fibroblasts from two newborns indicated enzymatic IBD defect. Molecular genetic analysis revealed seven new rare variations in the IBD gene (c.348C>A, c.400G>T, c.409G>A, c.455T>C, c.958G>A, c.1000C>T and c.1154G>A). Furthermore, sequence analysis of the short-chain acyl-CoA dehydrogenase (SCAD) gene revealed heterozygosity for the prevalent c.625G>A susceptibility variation in all newborns and in the first reported IBD patient. Functional studies in isolated mitochondria demonstrated that the IBD variations present in the Danish newborn (c.409G>A and c.958G>A) together with a previously published IBD variation (c.905G>A) disturbed protein folding and reduced the levels of correctly folded IBD tetramers. Accordingly, low/no IBD residual enzyme activity was detectable when the variant IBD proteins were overexpressed in Chang cells.     

中、短链酰基辅酶A脱氢酶缺乏症患儿临床特点分析及基因突变研究

中、短链酰基辅酶A 脱氢酶缺乏症属脂肪酸β 氧化障碍疾病,其基因突变可导致中、短链脂肪酸无法进入线粒体进行氧化供能,引起多器官功能异常。本研究对2 例临床表现为低血糖合并代谢性酸中毒的患儿进行血酰基肉碱及尿液有机酸分析,同时对患儿及其父母进行基因突变检测。家系1 患儿,男,3 d,出生后因新生儿窒息、吸奶无力、嗜睡住院治疗。血酰基肉碱谱提示中链酰基肉碱（C6~C10）升高,其中辛酰肉碱（C8）3.52 μmol/L（参考值0.02~0.2 μmol/L）;尿有机酸分析未见明显异常;Sanger 测序发现ACADM 基因7 号外显子已报道纯合突变c.580A>G（p.Asn194Asp）。家系2 患儿,女,3 个月,因咳嗽伴反复发热10 余天住院治疗。血酰基肉碱谱提示血丁酰肉碱（C4）1.66 μmol/L（参考值0.06~0.6 μmol/L）;尿有机酸分析提示乙基丙二酸55.9（参考值0~6.2）;Sanger 测序发现ACADS 基因已报道纯合突变c.625G > A（p.Gly209Ser）。研究结果提示对不明原因代谢性酸中毒及低血糖患儿应进行遗传代谢病筛查,通过家系ACADM、ACADS 基因分析,将有助于中、短链酰基辅酶A 脱氢酶缺乏症的诊断。     

Melatonin state in Mendenhall's syndrome.

We report a case of Mendenhall''s syndrome that presented as hypoglycaemia. The clinical and biochemical features of the case are described including, for the first time, studies of melatonin state showing raised melatonin metabolite excretion in the urine as might be expected with disordered pineal function.     

A new case of short-chain acyl-CoA dehydrogenase deficiency with isolated ethylmalonic aciduria

A 28-month-old Turkish girl presented with recurrent bronchopneumonia and severe muscular hypotonia. Urinary excretion of ethylmalonic acid was persistently elevated, methylsuccinate appearing only in stress situations. Studies in cultured fibroblasts showed a deficiency of short-chain acyl-CoA dehydrogenase.     

Short-chain hydroxyacyl-coenzyme A dehydrogenase deficiency presenting as unexpected infant death: A family study

We describe a case of liver-specific short-chain hydroxyacyl-coenzyme A dehydrogenase deficiency. Enzymatic confirmation of heterozygosity was shown in family members, illustrating the recessive nature of this new disorder. Heterozygous carriers did not present with biochemical abnormalities when challenged by fasting.     

Hyperexcretion of homocitrulline in a Malaysian patient with lysinuric protein intolerance

Lysinuric protein intolerance (LPI; MIM 222700) is an inherited aminoaciduria with an autosomal recessive mode of inheritance. Biochemically, affected patients present with increased excretion of the cationic amino acids: lysine, arginine, and ornithine. We report the first case of LPI diagnosed in Malaysia presented with excessive excretion of homocitrulline. The patient was a 4-year-old male who presented with delayed milestones, recurrent diarrhea, and severe failure to thrive. He developed hyperammonemic coma following a forced protein-rich diet. Plasma amino acid analysis showed increased glutamine, alanine, and citrulline but decreased lysine, arginine and ornithine. Urine amino acids showed a marked excretion of lysine and ornithine together with a large peak of unknown metabolite which was subsequently identified as homocitrulline by tandem mass spectrometry. Molecular analysis confirmed a previously unreported homozygous mutation at exon 1 (235 G?>?A, p.Gly79Arg) in the SLC7A7 gene. This report demonstrates a novel mutation in the SLC7A7 gene in this rare inborn error of diamino acid metabolism. It also highlights the importance of early and efficient treatment of infections and dehydration in these patients. Conclusion: The diagnosis of LPI is usually not suspected by clinical findings alone, and specific laboratory investigations and molecular analysis are important to get a definitive diagnosis.