Successful Domino Liver Transplantation from a Patient with Methylmalonic Acidemia.

Liver transplantation has been reported in patients with methylmalonic acidemia (MMA), but long-term outcome is controversial. Many patients with other approved indications for liver transplantation die before donor grafts are available. A 28-year-old man with MMA underwent cadaveric liver transplantation. His liver was used as a domino graft for a 61-year-old man with primary sclerosing cholangitis, who had low priority on the transplant waiting list. Surgical outcome was successful, and after transplantation both patients have excellent graft function. The patient with MMA showed substantial decrease in methylmalonate in urine (from 5,277 ± 1,968 preoperatively to 1,068 ± 384 mmol/mol creatinine) and plasma (from 445.9 ± 257.0 to 333.3 ± 117.7 µmol/l) over >1-year follow-up, while dietary protein intake increased from 0.6 to 1.36 ± 0.33 g/kg/day. The domino recipient maintained near-normal levels of plasma amino acids but did develop elevated methylmalonate in blood and urine while receiving an unrestricted diet (peak plasma methylmalonate 119 µmol/l and urine methylmalonate 84-209 mmol/mol creatinine, with 1.0-1.9 g/kg/day protein). Neither patient demonstrated any apparent symptoms of MMA or metabolic decompensation during the postoperative period or following discharge. CONCLUSION: Liver transplantation substantially corrects methylmalonate metabolism in MMA and greatly attenuates the disease. In this single patient experience, a liver from a patient with MMA functioned well as domino graft although it did result in subclinical methylmalonic acidemia and aciduria in the recipient. Patients with MMA can be considered as domino liver donors for patients who might otherwise spend long times waiting for liver transplantation.

Positive newborn screen in the biochemically normal infant of a mother with treated holocarboxylase synthetase deficiency.

Expanded programmes of newborn screening permit early diagnosis in time to prevent serious complications. These programmes have begun to detect patients who might otherwise remain asymptomatic. An additional confounding variable is the positive screen that results from maternal rather than neonatal disease. This was the case in an infant in whom elevated hydroxyisovalerylcarnitine (C(5)OH) in his newborn screen was the result of placental transfer from his mother, whose holocarboxylase synthetase deficiency was being successfully treated with biotin. The mother had been diagnosed and treated with biotin prenatally. She had no phenotypic feature of holocarboxylase synthetase deficiency, most importantly no episodes ever of acute metabolic acidosis. In the infant a repeat screen was also positive. On day 28 the infant's plasma C(5)OH carnitine was 0.05 mumol/L (normal) and urinary organic acids on day 39 were normal. The mother's excretion of 3-hydroxyisovaleric acid was 109 mmol/mol creatinine. These observations indicate that holocarboxylase synthetase deficiency is one more maternal metabolic disease which may lead to a positive screen in her unaffected newborn infant. They also make the point that holocarboxylase synthetase deficiency in an infant should be detectable in programmes of neonatal screening, which was not clear previously.

Unusual presentation of propionic acidaemia as isolated cardiomyopathy.

Propionic acidaemia (PA) is an autosomal recessive disease that results from deficiency of propionyl-CoA carboxylase (PCC). In the majority of reported cases, the phenotype includes metabolic acidosis and/or neurological deficits. We report on a 14-year-old Asian-American male with PA who presented with isolated cardiomyopathy without any documented episodes of metabolic acidosis or evidence of any neurocognitive deficits. On routine metabolic screening, the patient was found to have urine organic acids suggestive of PA. Biochemical and genetic characterization confirmed a PCC deficiency with two novel mutations in PCCB: IVS7 + 2 T > G (c.763 + 2 T > G) and p.R410Q (c.1229 G > A). Residual enzyme activity likely explains our patient's mild phenotype. Splicing mutations tend to result in a milder phenotype as these mutations may still produce small amounts of normal enzyme. In addition, the similar p.R410W mutation has been shown to have partial residual activity. Moreover, this case illustrates that a thorough metabolic evaluation should be performed in both paediatric and adult patients with cardiomyopathy. Such an evaluation has important implications for clinical management and genetic counselling.

Expanded clinical and molecular spectrum of guanidinoacetate methyltransferase (GAMT) deficiency.

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine biosynthesis, characterized by excessive amounts of guanidinoacetate in body fluids, deficiency of creatine in the brain, and presence of mutations in the GAMT gene. We present here 8 new patients with GAMT deficiency along with their clinical, biochemical and molecular data. The age at diagnosis of our patients ranges from 0 to 14 years. The age of onset of seizures usually ranges from infancy to 3 years. However, one of our patients developed seizures at age 5; progressing to myoclonic epilepsy at age 8 years and another patient has not developed seizures at age 17 years. Five novel mutations were identified: c.37ins26 (p.G13PfsX38), c.403G>T (p.D135Y), c.507_521dup15 (p.C169_S173dup), c.402C>G (p.Y134X) and c.610_611delAGinsGAA (p.R204EfsX63). Six patients had the c.327G>A (last nucleotide of exon 2) splice-site mutation which suggests that this is one of the most common mutations in the GAMT gene, second only to the known Portuguese founder mutation, c.59G>C (p.W20S). Our data suggests that the clinical presentation can be variable and the diagnosis may be overlooked due to unawareness of this disorder. Therefore, GAMT deficiency should be considered in the differential diagnosis of progressive myoclonic epilepsy as well as in unexplained developmental delay or regression with dystonia, even if the patient has no history of seizures. As more patients are reported, the prevalence of GAMT deficiency will become known and guidelines for prenatal diagnosis, newborn screening, presymptomatic testing and treatment, will need to be formulated.

Creatine kinase and uric acid: early warning for metabolic imbalance resulting from disorders of fatty acid oxidation.

UNLABELLED: In eight patients with disorders of fatty acid oxidation, analysis of uric acid and creatine kinase served as indicators of the underlying disorder in episodes of acute metabolic imbalance. Six patients had deficiency of medium-chain acyl-CoA dehydrogenase, one had long-chain hydroxyacyl-CoA dehydrogenase deficiency, and one very long-chain acyl-CoA dehydrogenase deficiency. The most common presentation was with symptomatic hypoglycemia; there was one Reye-like presentation and one of rhabdomyolysis. The mechanism of the elevation of uric acid and creatine kinase appears to be the breakdown of tissue. CONCLUSION: it is concluded that uric acid and creatine kinase provide a useful alerting signal to the presence of a disorder of fatty acid oxidation. Maximal levels of uric acid in this series were 6.2-21.5 mg/dl and of creatine kinase 879-27,557 U/l.

Mitochondrial tubulopathy: the many faces of mitochondrial disorders.

We report a rare presentation of mitochondrial disorder in a child with recurrent carpopedal spasms due to hypocalcemia and hypomagnesemia, secondary to renal proximal tubulopathy and possible hypoparathyroidism. At least two mutant mitochondrial DNA species were identified, and abnormal mitochondria were found in the muscle and renal biopsy specimens. The case illustrates the spectrum and diversity of mitochondrial presentations, arising because of heteroplasmy of mutations and the type of organs affected.

Nerve conduction changes in patients with mitochondrial diseases treated with dichloroacetate.

Serial measurements of nerve conduction velocities and amplitudes were performed in 27 patients with congenital lactic acidemia over 1 year of sodium dichloroacetate (DCA) administration. Patients were treated with oral thiamine (100 mg) and DCA (initial dose of 50 mg/kg) daily. Nerve conduction velocity and response amplitude were measured in the median, radial, tibial, and sural nerves at 0, 3, 6, and 12 months, and plasma DCA pharmacokinetics were measured at 3 and 12 months. Baseline electrophysiologic parameters in this population were generally below normal but as a group were within 2 standard deviations of normal means. Although symptoms of neuropathy were reported by only three patients or their families, nerve conduction declined in 12 patients with normal baseline studies, and worsening of nerve conduction occurred in the two who had abnormalities at baseline. Peripheral neuropathy appears to be a common side effect during chronic DCA treatment, even with coadministration of oral thiamine. Nerve conduction should be monitored during DCA treatment.

Autism associated with the mitochondrial DNA G8363A transfer RNA(Lys) mutation.

We report a family with a heterogeneous group of neurologic disorders associated with the mitochondrial DNA G8363A transfer ribonucleic acid (RNA)Lys mutation. The phenotype of one child in the family was consistent with autism. During his second year of life, he lost previously acquired language skills and developed marked hyperactivity with toe-walking, abnormal reciprocal social interaction, stereotyped mannerisms, restricted interests, self-injurious behavior, and seizures. Brain magnetic resonance imaging (MRI) and repeated serum lactate studies were normal. His older sister developed signs of Leigh syndrome with progressive ataxia, myoclonus, seizures, and cognitive regression. Her laboratory studies revealed increased MRI T2-weighted signal in the putamen and posterior medulla, elevated lactate in serum and cerebrospinal fluid, and absence of cytochrome c oxidase staining in muscle histochemistry. Molecular analysis in her revealed the G8363A mutation of the mitochondrial transfer RNA(Lys) gene in blood (82% mutant mitochondrial DNA) and muscle (86%). The proportions of mutant mitochondrial DNA from her brother with autism were lower (blood 60%, muscle 61%). It is likely that the origin of his autism phenotype is the pathogenic G8363A mitochondrial DNA mutation. This observation suggests that certain mitochondrial point mutations could be the basis for autism in some individuals.

Kearns-Sayre syndrome presenting as 2-oxoadipic aciduria.

A patient with 2-oxoadipic aciduria and 2-aminoadipic aciduria presented at 2 years of age with manifestations typical of organic acidemia, episodes of ketosis and acidosis, progressive to coma. This resolved and the key metabolites disappeared from the urine and blood. At 9 years of age she developed typical Kearns-Sayre syndrome with complete heart block, retinopathy, and ophthalmoplegia. Southern blot revealed a deletion in the mitochondrial genome.

Malonic aciduria in Maltese dogs: normal methylmalonic acid concentrations and malonyl-CoA decarboxylase activity in fibroblasts.

A family of Maltese dogs with malonic aciduria is reported. The propositus presented at 3 years of age with episodes of seizures and stupor with hypoglycaemia, acidosis, and ketonuria. Urinary organic acid assays showed elevated malonic acid without elevation of methylmalonic acid. Cultured fibroblasts had normal malonyl-CoA decarboxylase activity. Treatment with frequent feedings of a low-fat diet high in medium-chain triglycerides resulted in normalization of clinical signs and a resolution of the malonic aciduria. Two full siblings of the propositus had died at a young age of undiagnosed metabolic and neurological disease. Urine organic acid assays were performed on other family members. A half-sister showed mild malonic aciduria and other organic acid changes similar to the propositus, while the mother and half-brother showed mildly elevated ketone bodies. This family suggests further genetic and clinical heterogeneity in the malonic acidurias.

Sensitive assay for mitochondrial DNA polymerase gamma.

BACKGROUND: The mitochondrial DNA polymerase gamma is the principal polymerase required for mitochondrial DNA replication. Primary or secondary deficiencies in the activity of DNA polymerase gamma may lead to mitochondrial DNA depletion. We describe a sensitive and robust clinical assay for this enzyme. METHODS: The assay was performed on mitochondria isolated from skeletal muscle biopsies. High-molecular weight polynucleotide reaction products were captured on ion-exchange paper, examined qualitatively by autoradiography, and quantified by scintillation counting. RESULTS: Kinetic analysis of DNA polymerase gamma by this method showed a K(m) for dTTP of 1.43 micromol/L and a K(i) for azidothymidine triphosphate of 0.861 micromol/L. The assay was linear from 0.1 to 2 microgram of mitochondrial protein. The detection limit was 30 units (30 fmol dTMP incorporated in 30 min). The linear dynamic range was three orders of magnitude; 30-30 000 units. Imprecision (CV) was 6.4% within day and 12% between days. Application of this assay to a mixed population of 38 patients referred for evaluation of mitochondrial disease revealed a distribution with a range of 0-2506 U/microgram, reflecting extensive biologic variation among patients with neuromuscular disease. CONCLUSION: This assay provides a useful adjunct to current laboratory methods for the evaluation of patients with suspected mitochondrial DNA depletion syndromes.

Mitochondrial DNA polymerase gamma deficiency and mtDNA depletion in a child with Alpers' syndrome.

Deficiency of mitochondrial DNA polymerase gamma activity was found in a patient with mtDNA depletion and Alpers' syndrome. Metabolic evaluation revealed fasting hypoglycemia, dicarboxylic aciduria, and reduced activity of the electron transport chain in skeletal muscle. The patient died in early childhood of fulminant hepatic failure, refractory epilepsy, lactic acidemia, and coma. mtDNA content was 30% of normal in skeletal muscle and 25% in the liver. The activity of mtDNA polymerase gamma was undetectable.

Analysis of organic acids, amino acids, and carnitine in dogs with lipid storage myopathy.

Abnormal accumulations of lipid droplets, localized predominantly in histochemical type 1 fibers, were observed in fresh frozen sections of muscle biopsies from 25 dogs with myalgia, weakness, and muscle atrophy. Compared to controls, lactic acidemia, hyperalaninemia, lactic and pyruvic aciduria, variably increased urinary excretion of carnitine esters, and muscle carnitine deficiency were present. These findings support a metabolic block in oxidative metabolism resulting in lactic acidemia in dogs with lipid storage myopathy.

Treatment of the acute crisis in maple syrup urine disease.

BACKGROUND: The acute crisis of metabolic decompensation in maple syrup urine disease is a potentially lethal medical emergency that requires reduction in concentrations of leucine and other branched-chain amino acids in plasma. Experience with intravenous mixtures of amino acids indicates that this can be accomplished by the synthetic forces of protein synthesis. However, these intravenous mixtures are not generally available. OBJECTIVE: To develop enteral mixtures suitable for administration by nasogastric drip in minimal volume. DESIGN: Mixtures of amino acids were designed containing no leucine, isoleucine, or valine for administration by nasogastric drip. Needs for water and calories were to be met intravenously. They were designed to be used in the management of the acute crisis. SETTING: Inpatient pediatric service. PATIENTS: Two patients with maple syrup urine disease. Data were collected during the management of 3 episodes of metabolic imbalance. INTERVENTION: Studies were carried out for 4 to 11 days, during which there was no intake of leucine. Four different mixtures were used and a fifth was designed on the basis of this experience. MAIN OUTCOME MEASURES: Effects on the concentrations of leucine and the other branched-chain amino acids. Clinical status closely mirrored the concentration of leucine. RESULTS: In each instance, a progressive fall in leucine concentration was obtained. Rates of fall were comparable to those obtained with intravenous therapy. Concentrations of isoleucine fell to levels that made this amino acid limiting for protein synthesis and hence therapeutic effect. This led to greater and earlier supplementation with isoleucine. Valine supplementation was also useful. CONCLUSIONS: The acute crisis of metabolic imbalance in maple syrup urine disease may be effectively treated by the continuous intragastric drip of solutions of amino acids devoid of leucine along with provision of water and calories intravenously.

Oxidative metabolism in Rett syndrome: 1. Clinical studies.

The etiology of Rett syndrome (RS) remains a mystery. The clinical phenotype has similarities to that of patients with mitochondrial defects of oxidative metabolism. There is evidence of lactate and pyruvate elevations in blood and CSF in some patients. Over the last 10 years we have studied girls with RS looking for evidence of a defect in oxidative metabolism. We present data on lactate and pyruvate blood measurements in 30 patients with RS with repeated measurements performed over time in many. Taken as a whole the means of measurements of lactate and pyruvate fall within the control range, however, individual patients have marked elevation of both lactate and pyruvate with considerable fluctuation over time. Nine girls with typical RS were studied in detail using a clinical protocol designed to identify disorders of oxidative metabolism. These patients underwent fasting for 24 hours, glucose loading and alanine loading tests. Seven girls had skin and muscle biopsies performed. One patient admitted with particularly high blood lactate levels underwent hourly blood collections over a 24 hour period during which state of alertness was noted and respiratory monitoring was performed. In this patient serial blood sampling for lactate performed. In this patient serial blood sampling for lactate performed with oxypneumocardiogram recording demonstrated a fall in plasma lactate to normal levels during sleep when the respiratory pattern was normal. Such fluctuations of plasma lactate apparently correlated with sleep/wake state and respiration suggest that in some patients with RS lactate elevations may arise from respiratory abnormalities. Other positive findings included prediabetic glucose responses in three girls. Ammonia levels following alanine loading were normal in all patients.

Anabolic effect of human growth hormone: management of inherited disorders of catabolic pathways.

The effects of growth hormone treatment and dietary alanine supplementation, individually and in combination, were studied in five patients with organic acidemias. Three patients had propionic acidemia, one had 3-hydroxyisobutyric acidemia, and one had a defect in isoleucine metabolism. Two patients with propionic acidemia had decreased growth hormone secretion in response to provocative stimuli (intravenous L-arginine and oral levodopa or clonidine); the remaining subjects had sufficient growth hormone secretion. Three of four subjects in whom IGF1 was measured showed subnormal concentrations at baseline (including two with normal growth hormone secretory responses). All patients showed an increase in linear growth with growth hormone. In the four patients studied, all had a significant increase in nitrogen retention over baseline with alanine or growth hormone alone, or with the combination of growth hormone and alanine, with a much greater effect of growth hormone. Lean body mass and body fat composition tended to become normal with treatment. Protein tolerance increased, and when the patients' dietary protein intakes were increased between 20 and 60% they maintained positive nitrogen balance, without a significant increase in metabolite excretion. One patient with propionic acidemia expired during the time of the study, following a course of recurrent pancreatitis and an episode of acute basal ganglia infarction. All of the other subjects showed clinical improvement (decreased incidence of ketoacidotic episodes and decreased frequency of hospital admission and school absence) during treatment, and even the patient who expired remained metabolically stable up to and through the terminal event. We conclude that growth hormone may be of value in the management of patients with organic acidemia.