Incidence of maple syrup urine disease in Portugal

Maple syrup urine disease is an autosomal recessive disorder of branched-chain amino acids metabolism with a worldwide frequency of 1/185,000 live newborns. In Portugal, the incidence of the disease has not been assessed. Based on the review of the cases diagnosed by tandem mass spectrometry an incidence of 1/86,800 live newborns was estimated in Portugal, indicating that the disease is more frequent in this country than reported in most populations.

Pyruvate dehydrogenase deficiency: identification of a novel mutation in the PDHA1 gene which responds to amino acid supplementation

The pyruvate dehydrogenase complex (PDHc) is an intramitochondrial multienzyme system, which plays a key role in aerobic glucose metabolism by catalysing the oxidative decarboxylation of pyruvate to acetyl-CoA. Genetic defects in the PDHc lead to lactic acidemia and neurological abnormalities. In the majority of the cases, the defect appears to reside in the E(1)alpha subunit, the first catalytic component of the complex. The report is on a 6-year-old Portuguese boy with mild neurological involvement and low PDHc activity with absence of E1alpha on immunoblotting analysis. Molecular studies showed a novel and "de novo" mutation in the PDHA1 gene, R253G. Treatment with arginine aspartate showed complete clinical and biochemical recovery. We hypothesise that arginine aspartate acts as a chemical or pharmacological chaperone, and suggest amino acid supplementation as a possible therapy in PDHA1 mutations with mild phenotypes.

CONCLUSION

our results encourage the use of amino acid supplementation to overcome the metabolic/biochemical changes induced by PDHA1 gene specific mutations associated with mild PDHc phenotypes.

Molecular and structural analyses of maple syrup urine disease and identification of a founder mutation in a Portuguese Gypsy community

Maple syrup urine disease (MSUD) is an autosomal recessive disorder, caused by the defective function of the branched-chain alpha-ketoacid dehydrogenase complex (BCKD). BCKD is a mitochondrial complex, encoded by four nuclear genes (BCKDHA, BCKDHB, DBT and DLD), involved in the metabolism of branched-chain amino acids (BCAAs). Since the MSUD mutational spectrum has not been previously assessed in Portugal, in this study we present the molecular characterization of 30 MSUD Portuguese patients. Seventeen putative mutations have been identified (six in BCKDHA, five in BCKDHB and six in DBT); seven of them are here described for the first time. The most common mutation identified was a C deletion in BCKDHA gene (c.117delC; p.R40GfsX23), already reported in the Spanish population. Interestingly, it was found in all patients of a Gypsy community from South of the country, so a founder effect is probably responsible for the high incidence of the disease in this community. Structural models of MSUD missense mutations have been performed to understand their pathogenic effect, in order to elucidate and often to predict the severity of a mutation clinical consequence.

Stereotypies in Rett syndrome: Analysis of 83 patients with and without detected MECP2 mutations

BACKGROUND

Hand stereotypies are considered a hallmark of Rett syndrome (RTT) and are usually described as symmetric movements at the midline. However, related pathologies may show the same type of involuntary movement. Furthermore, patients with RTT also have stereotypies with other localizations that are less well characterized.

METHODS

We analyzed stereotypies in 83 patients with RTT, 53 with and 30 without a mutation detected in the MECP2 gene. Patients were observed and videotaped always by the same pediatric neurologist. Stereotypies were classified, and data were submitted to statistical analysis for comparison of mutation-positive and -negative patients and analysis of their evolution with the disease.

RESULTS

All the patients showed hand stereotypies that coincided with or preceded the loss of purposeful hand movements in 62% of the patients with MECP2 mutations. The hair pulling stereotypy was more frequent in the group with detected mutations, whereas hand washing was not. Hand gaze was absent in all RTT patients with MECP2 mutations. Patients with MECP2 mutations also had more varied stereotypies, and the number of stereotypies displayed by each patient decreased significantly with age in this group. In all patients, stereotypies other than manual tended to disappear with the evolution of the disease.

CONCLUSIONS

Although symmetric midline hand stereotypies were not specific to patients with an MECP2 mutation, some of the other stereotypies seemed to be more characteristic of this group. In patients younger than 10 years and meeting the necessary diagnostic criteria of Rett syndrome, the association of hand stereotypies without hand gaze, bruxism, and two or more of the other stereotypies seemed to be highly indicative of the presence of an MECP2 mutation.

The correlation of genotype and phenotype in Portuguese hyperphenylalaninemic patients

To understand the basis for the clinical heterogeneity of phenylalanine hydroxylase deficiency among Portuguese hyperphenylalaninemic patients, genotype-phenotype correlations were established. A group of 61 patients was completely genotyped, leading to the identification of 20 different mutant alleles in 36 different genotypic combinations, including a mutant allele not reported previously. The severity of those mutations found within this hyperphenylalaninemic population, which have not been previously expressed in vitro, were assessed. The results obtained by the present study exhibit a strong correlation between the predicted residual enzyme activity, as deduced from the genotype of the patients, and the biochemical phenotype represented by the diagnostic parameters (phenylalanine levels before the beginning of treatment and the dietary phenylalanine tolerance). It was observed that only a judicious follow-up and compliance with the appropriate diet permits the correct assessment of the clinical phenotype of the patients. Additionally, based upon the correlation observed between genotypes and diagnostic parameters, it was possible to predict the potential residual enzyme activity of those mutations (identified in our patients) which have not yet been studied in vitro.

[Branched chain amino acid diseases]

The authors present 19 cases of branched-chain AA catabolism disease: 9 Maple Syrup Urine Diseases, 6 Methylmalonic Acidemias, 2 Propionic Acidemias, 1 case of 3-OH-3-methylglutaryl-CoA-lyase deficiency and another of 2-methyl-ketoacetyl-CoA-thiolase deficiency. Fifteen are early neonatal forms and in 4 the onset occurred later. Fifteen patients (78.9%) needed one or several extra-corporal procedures either in the initial acute phase or during relapse. Fifteen patients presented several metabolic relapses, sometimes fatal (3 children). Global mortality was 26.3%, that is 5/19 patients: 4 children with neonatal forms, one with a later onset. Eleven patients (57.9%) had an IQ/DQ > or = 80: only 46.6% of the neonatal forms obtained these results, in contrast with all the late onset forms. Of the survivors, 9 (64.2%), presented a residual neurologic condition. The correct diagnostic and treatment procedures are defined and the need to consider the existence of these diseases at any age, particularly in the neonatal period, is stressed.

A case of GM1 gangliosidosis type I

A six-month-old female gypsy child, the daughter of second degree cousins, born after a full-term pregnancy and normal delivery, is described. There was generalized neonatal edema. Abnormalities included psychomotor retardation from birth and progressive appearance of facial dysmorphism, organ enlargement, axial hypotonia, hypertonia in limbs, myoclonic jerks, optic atrophy and bilateral cherry-red spots. The diagnosis of GM1 type 1 gangliosidosis was confirmed by biochemical, enzymatic and ultrastructural findings.

[Phenylketonuria--physical and mental development of phenylketonuric children subjected to early treatment]

The Authors present the first clinical and laboratory assessment of 6 children with PKU, diagnosed and treated early, as a result of the application of the Early Diagnosis Programme in the southern part of the country, from April 1984 to November 1986. The main protein source used in the feeding of these patients was a phenylalanine-free mixture of amino-acids, with an excellent tolerance.