Mark Sharrard

Phosphoserine Aminotransferase Deficiency: A Novel Disorder of the Serine Biosynthesis Pathway

We present the first two identified cases of phosphoserine aminotransferase deficiency. This disorder of serine biosynthesis has been identified in two siblings who showed low concentrations of serine and glycine in plasma and cerebrospinal fluid. Clinically, the index patient presented with intractable seizures, acquired microcephaly, hypertonia, and psychomotor retardation and died at age 7 mo despite supplementation with serine (500 mg/kg/d) and glycine (200 mg/kg/d) from age 11 wk. The younger sibling received treatment from birth, which led to a normal outcome at age 3 years. Measurement of phosphoserine aminotransferase activity in cultured fibroblasts in the index patient was inconclusive, but mutational analysis revealed compound heterozygosity for two mutations in the PSAT1 gene--one frameshift mutation (c.delG107) and one missense mutation (c.299A-->C [p.Asp100Ala])--in both siblings. Expression studies of the p.Asp100Ala mutant protein revealed a V(max) of only 15% of that of the wild-type protein.

Carnitine-acylcarnitine translocase deficiency - a mild phenotype

A 15-month-old Pakistani child was admitted to hospital following a prolonged chronic convulsion. He had a depressed level of consciousness but physical examination was otherwise unremarkable. Plasma glucose was 1mmol/L and his urine contained no ketones. His condition improved rapidly with intravenous glucose. His parents are first cousins and his two older siblings are healthy. He had suffered two previous prolonged tonic febrile fits, during which his blood glucose had not been measured. On admission, his plasma lactate was 1.7mmol/L. Further investigations showed a plasma total carnitine of 13μmol/L (normal 23–60) and free carnitine of 4μmol/L (normal 15–53). Urine acylcarnitine was high (60μmol/mmol creatinine; normal 1.0–14.0) and urine free carnitine was low at <1.0μmol/mmol creatinine (normal 4.0–29.0). Serum insulin was appropriately low (0.6mU/L). Urine organic acids showed a hypoketotic dicarboxylic aciduria with prominent excretion of adipate and suberate. The sebacate to adipate ratio was <0.2. A small peak of suberylglycine was detected. He was put on a highcarbohydrate, low-fat diet with frequent feeds and L-carnitine 100mg/kg body weight per day, with the recommendation that he should not fast for more than 8h, subsequently amended to 6h. Dietary long-chain fat was set at a limit of 10g/day (estimation of previous long-chain fat intake was 40g/day) with medium-chain triglyceride supplementation and frequent high-carbohydrate feeds. He is now 20 years old and apart from two brief admissions to hospital during intercurrent infections, the most recent following a hypoglycaemic fit, his growth and development are normal. His cardiac function, as measured by ultrasonography, has remained normal throughout. Measurement of β-oxidation rates by the method of Manning and colleagues (1990) gave mean residual activities, as compared to simultaneous controls for [9,10-3H]myristate, [9,10-3H]palmitate and [9,10-3H]oleate, of 19%, 15%, 15% and 18%, 17% 14% for fibroblasts and lymphocytes, respectively. Measurement of carnitine-acylcarnitine translocase (McKusick 212138) activity by the method of Pande and colleagues (1993) gave 0.10 ±0.038 (8 repeats) vs 1.74±0.46 (n=9) nmol/min per kg protein for patient and controls, respectively. There have been six previous reports of carnitine-acylcarnitine translocase deficiency. All of these cases have had a severe phenotype with generally undetectable enzyme activity and very low β-oxidation flux. All of these patient have had a fatal outcome, most in the neonatal period, although one child survived to 3 years with early medical intervention. Our patient gave a mean residual carnitine-acylcarnitine translocase activity of 6% of controls and a mean residual β-oxidation activity in lymphocytes and fibroblasts of 16%. J. Inher. Metab. Dis. 20 (1997) 000–000

Magnetic resonance spectroscopy changes following haemopoietic stem cell transplantation in children with cerebral adrenoleukodystrophy.

X‐linked cerebral adrenoleukodystrophy is an aggressive, rapidly progressive disorder resulting in considerable morbidity and, left untreated, mortality. Patients typically present before the age of 10 years with progressive symptomatology including ataxia, spasticity, and focal neurological deficits. Current therapeutic options are limited, the treatment of choice being haemopoietic stem cell transplantation (HSCT). Intervention is beneficial to those children with early disease and characteristic magnetic resonance (MR) imaging changes. Developments in MR imaging have led to the incorporation of MR spectroscopy in the assessment tools; however, it is yet to be included in stratified assessment tools to guide treatment choice. Furthermore, there remains a paucity of outcome data on MR spectroscopy changes following HSCT. We describe our experience in two males with confirmed cerebral adrenoleukodystrophy treated, at the mean age of 5 years 6 months, with HSCT and report the pronounced spectroscopic changes observed following treatment. Both children, observed for a minimum period of 14 months following treatment, demonstrate complete reversal in previously deteriorating spectroscopy with marked increase in N‐acetyl‐aspartate (NAA)/choline (Cho) ratios and reduction in Cho/creatine (Cr) ratios following HSCT treatment with concomitant stabilization of clinical status.

The use of MR imaging and spectroscopy of the brain in children investigated for developmental delay: What is the most appropriate imaging strategy?

ObjectivesDevelopmental delay is a common problem in paediatric practice and many children with developmental delay are referred for MR imaging. Our study was performed as part of a continuing audit process to optimise our MR protocol and case selection.Materials and methodsWe performed MR imaging and spectroscopy protocol on 157 children with developmental delay. We analysed the effect of these interventions by looking at the overall detection rate of relevant pathology and in particular subgroups of the children.Results71% of the children had normal MR imaging, 10% had non-specific findings and 19% had specific abnormalities on MR imaging. The overall risk of having a specific structural abnormality with isolated developmental was 7.5% but if other neurological symptoms/signs were present the risk was 28%. Two children had abnormal spectroscopic findings, one with tuberous sclerosis and the other with absent brain creatine.ConclusionCase selection for MR imaging is important in children with developmental delay. The best strategies for selecting children for MR are either; not performing MR with developmental delay in one domain only or performing MR with developmental delay in three or four domains or if there are other neurological features.

Normal acylcarnitines in maternal urine during a pregnancy affected by glutaric aciduria type II

Normal acylcarnitines in maternal urine during a pregnancy a†ected by glutaric aciduria type II N. J. Manning1*, J. R. Bonham1, M. Downing1, R. G. Edwards1, S. E. Olpin1, R. J. Pollitt1, M. Pourfarzam3, M. J. Sharrard2 and M. S. T anner2 1 Department of Chemical Pathology and Neonatal Screening, 2 Department of Paediatrics, The ChildrenÏs Hospital, Sheffield ; 3 Department of Child Health, The Royal Victoria InÐrmary, Newcastle upon Tyne, UK * Correspondence : Department of Chemical Pathology and Neonatal Screening, The ChildrenÏs Hospital, Western Bank, Sheffield S10 2TH, UK

Unilateral periventricular leukomalacia in association with pyruvate dehydrogenase deficiency.

Pyruvate dehydrogenase (PDH) deficiency is a major cause of primary lactic acidosis and neurological dysfunction in infancy and early childhood. A deficiency of PDH E1 alpha, a subunit of the PDH complex, is a prominent cause of congenital lactic acidosis. We describe a female infant born at term and delivered by emergency Caesarean section because of fetal distress. There was no parental consanguinity. She presented at 5 months of age with failure to thrive, microcephaly, hypertonia, and developmental impairment. Her plasma and cerebrospinal fluid lactate were raised. She had raised plasma pyruvate with a normal lactate–pyruvate ratio. Magnetic resonance imaging of the brain showed a focal dilatation of the right lateral ventricle with unilateral periventricular leukomalacia (PVL) with subependymal cyst. Skin fibroblast culture assay revealed PDH deficiency, confirmed by mutation analysis of the E1 alpha subunit. At 18 months of age, she has hypertonia and global impairment and is making slow progress. Denver II assessment showed delay in gross motor, fine motor, adaptive, personal, social, and language categories. She has been treated with dichloroacetate and a ketogenic diet since the age of 10 and 13 months respectively, without any side effects. To our knowledge, unilateral PVL as a neuroradiological feature has not been described in children with PDH deficiency. PDH deficiency should be considered as a differential diagnosis if PVL is unilateral and if the perinatal history is not typical of PVL.

Acute bilateral striatal necrosis with rotavirus gastroenteritis and inborn metabolic predisposition.

We present a 9‐month‐old male with acute rotavirus gastroenteritis who developed an acute encephalopathy with focal seizures and developmental regression. Magnetic resonance imaging showed bilateral striatal necrosis and raised glutarylcarnitine levels on tandem mass spectrometry of a (crisis) blood spot, and chromatography of organic acids revealed increased urinary excretion of dicarboxylic acid. Skin biopsy demonstrated a partial decrease in glutaryl‐CoA dehydrogenase activity. The case was not typical for either rotavirus encephalitis/rotavirus‐associated encephalopathy or for glutaric aciduria type I. The patient has developmental delay and continues to receive physiotherapy, speech therapy, and local developmental follow‐up.

Riboflavin-Responsive Trimethylaminuria in a Patient with Homocystinuria on Betaine Therapy

A 17-year-old female patient with pyridoxine non-responsive homocystinuria, treated with 20 g of betaine per day, developed a strong body odour, which was described as fish-like. Urinary trimethylamine (TMA) was measured and found to be markedly increased. DNA mutation analysis revealed homozygosity for a common allelic variant in the gene coding for the TMA oxidising enzyme FMO3. Without changing diet or betaine therapy, riboflavin was given at a dose of 200 mg per day. An immediate improvement in her odour was noticed by her friends and family and urinary TMA was noted to be greatly reduced, although still above the normal range.Gradual further reductions in TMA (and odour) have followed whilst receiving riboflavin. Throughout this period, betaine compliance has been demonstrated by the measurement of dimethylglycine (DMG) excretion, which has been consistently increased. Marked excretions of DMG when the odour had subsided also demonstrate that DMG was not the source of the odour.This patient study raises the possibility that betaine may be converted to TMA by intestinal flora to some degree, resulting in a significant fish odour when oxidation of TMA is compromised by FMO3 variants. The possibility exists that the body odour occasionally associated with betaine therapy for homocystinuria may not be related to increased circulating betaine or DMG, but due to a common FMO3 mutation resulting in TMAU. Benefits of riboflavin therapy for TMAU for such patients would allow the maintenance of betaine therapy without problematic body odour.

Clinical presentation of mitochondrial diseases in children with progressive intellectual and neurological deterioration

Verity et al. describe 2493 patients with progressive intellectual and neurological deterioration (PIND) identified over 11 years. An expert panel determined a diagnosis in 1047 patients. Overall, 112 (4.5%) had an underlying mitochondrial disease, and 40 of these had died, giving an overall point prevalence for children with PIND and mitochondrial disease of 0.62 per 100 000 of the paediatric population. This figure includes patients with pyruvate dehydrogenase deficiency who are not always included in mitochondrial disease prevalence studies. Childhood mitochondrial disease prevalence has been estimated at 3 to 6.2 per 100 000 with a point prevalence in Sweden of mitochondrial encephalomyopathies in children of 4.8 per 100 000. Verity et al. explain their low prevalence in terms of under-ascertainment and that not all patients with mitochondrial disease experience PIND. Also, patients were investigated in a number of centres and not necessarily in a uniform or systematic manner and Verity et al. do not state how many patients with PIND were investigated for mitochondrial disease. Any study of the prevalence of mitochondrial disease is likely to be an underestimate as there is no screening test with high sensitivity and definitive diagnostic tests are not readily available for many potential disorders, notably deficiencies of complex V and many nuclear DNA mutations. The majority of children with mitochondrial disease present with or exhibit neurological manifestations. In a childhood mitochondrial disease population in the US, 60% presented with neuromuscular features and 40% with cardiac features although 20% of the cardiac group also had developmental delay. Two studies examined intellectual and neurological deterioration in children presenting with mitochondrial encephalomyopathies and found progressive deterioration in 58 to 60%. Combining these figures, admittedly from different populations, the prevalence of mitochondrial disease and PIND would be expected to be 1 to 2.5 per 100 000. In a defined Finnish paediatric population, Uusimaa et al. found 15% of patients with encephalomyopathy or myopathy had a probable mitochondrial disease. Not all would show progressive deterioration. In those who had mitochondrial DNA (mtDNA) sequenced, 18% (mtDNA) had mtDNA mutations, whereas Verity et al. found DNA mutations in 70% of those examined, 60% of these in mtDNA, mostly in the ATPase 6 gene. All the mtDNA mutations in the Finnish study were in mitochondrial RNA genes. Verity et al. found 10 children (20% of those tested or 9% of the mitochondrial PIND group overall) with mutations in the SURF1 gene whereas in a Swedish study of Leigh disease, no patient had SURF1 mutations. Ethnicity is a significant variable in molecular analysis of mitochondrial disease. Verity et al. examined the link between PIND, mitochondrial disease, vaccination, and autism. This association is particularly topical because of a 19-month-old female in the US, described in the literature by her father. She developed autistic features after vaccination and a subsequent febrile illness, and was later found to have a mitochondrial disorder. Her parents sued the Department of Health and Human Services for compensation under the Vaccine Injury Compensation Program and won. Neurological regression is a common feature of autism, usually occurring before 3 years of age. A number of studies have demonstrated an increased prevalence of mitochondrial disorders in patients with autistic features. In children with autism associated with hypotonia, epilepsy, and developmental delay (HEADD syndrome), respiratory chain abnormalities and mtDNA mutations are especially prevalent. Weissman et al. studied 25 children with autistic features and mitochondrial disease diagnosed by respiratory chain complex deficiency or mtDNA mutation analysis. This group showed features not typical of idiopathic autism, with a high incidence of fatigability, early gross motor delay, or atypical regressions, either multiple or occurring after the age of 3 years. These clinical features may allow selection of patients with autism for investigation of mitochondrial disorders. One of these patients was the one described with the vaccination reaction. The authors point out that temporal relation does not prove causation. Verity et al. describe three patients with autistic features. In two of these patients there was a temporal relationship between the onset of clinical symptoms and vaccination, although one of these patients simultaneously experienced Norwalk virus infection. Deterioration in patients with mitochondrial disease is frequently precipitated by infective illness. Weismann et al. point out that vaccination and infection may both provide a non-specific stress that may provoke deterioration in an infant with a mitochondrial disease, and this could be associated with the appearance of autistic features. Around 50% of Verity et al.’s cases presented during the first year of life, a time when there is likely to be a temporal relationship with vaccination, and also febrile viral illness. The extent to which vaccination will be blamed for deterioration in mitochondrial disease remains to be seen.

P04.11 Unilateral Periventricular Leucomalacia in Association with Pyruvate Dehydrogenase Deficiency

ABBREVIATIONS PDH Pyruvate dehydrogenase PVL Periventricular leukomalacia Pyruvate dehydrogenase (PDH) deficiency is a major cause of primary lactic acidosis and neurological dysfunction in infancy and early childhood. A deficiency of PDH E1 alpha, a subunit of the PDH complex, is a prominent cause of congenital lactic acidosis. We describe a female infant born at term and delivered by emergency Caesarean section because of fetal distress. There was no parental consanguinity. She presented at 5 months of age with failure to thrive, microcephaly, hypertonia, and developmental impairment. Her plasma and cerebrospinal fluid lactate were raised. She had raised plasma pyruvate with a normal lactate–pyruvate ratio. Magnetic resonance imaging of the brain showed a focal dilatation of the right lateral ventricle with unilateral periventricular leukomalacia (PVL) with subependymal cyst. Skin fibroblast culture assay revealed PDH deficiency, confirmed by mutation analysis of the E1 alpha subunit. At 18 months of age, she has hypertonia and global impairment and is making slow progress. Denver II assessment showed delay in gross motor, fine motor, adaptive, personal, social, and language categories. She has been treated with dichloroacetate and a ketogenic diet since the age of 10 and 13 months respectively, without any side effects. To our knowledge, unilateral PVL as a neuroradiological feature has not been described in children with PDH deficiency. PDH deficiency should be considered as a differential diagnosis if PVL is unilateral and if the perinatal history is not typical of PVL.