Intermediate maple syrup urine disease: neuroimaging observations in 3 patients from South India.

Maple syrup urine disease is a disorder of branched-chain keto acid metabolism. Three children were diagnosed with the intermediate form of maple syrup urine disease during routine evaluation of mental retardation. Clinical features were characterized by mental retardation, seizures, autistic features, and movement disorder in the form of dystonia. High-performance liquid chromatography of the urine and serum revealed elevated levels of branched-chain amino acids, suggesting a diagnosis of maple syrup urine disease. Magnetic resonance imaging showed diffuse hyperintense signals in the white matter along with involvement of the thalami and globus pallidus. Magnetic resonance imaging in the intermediate form showed myelination in the posterior limb of the internal capsule, in contrast to the classic form of the disease. Knowledge about the neuroimaging findings of this rare disease will help to narrow down the differential diagnosis when evaluating children with unexplained mental retardation and seizures.

Actualización en el tratamiento agudo y crónico de la enfermedad orina olor a jarabe de arce de presentación neonatal / Update acute treatment and follow up of neonatal maple syrup urine disease

La enfermedad de la orina olor a jarabe de arce se produce por un defecto del complejo enzimático deshidrogenasa de los a-cetoácidos, acumulándose valina, isoleucina y leucina (VIL) y de sus metabolitos asociados a neurotoxicidad. Su herencia es autosómica recesiva y la incidencia varía de 1:290.000 a 1:200 recién nacidos. La forma más frecuente es la forma neonatal o clásica, que se manifiesta desde el 5º día de vida con rechazo de la alimentación, somnolencia y coma. Si no se diagnostica y trata a tiempo, los pacientes fallecen. El tratamiento durante la descompensación consiste en terapia intensiva nutricional para evitar catabolismo y disminuir la concentración plasmática de leucina bajo 200 µM/L. En el período crónico se entrega una dieta restringida en VIL, se suplementa con leche especial sin VIL, y aminoácidos libres (L-valina, L-isoleucina) y tiamina. Diversos estudios han demostrado que existe una estrecha correlación entre la edad de diagnóstico, control metabólico a largo plazo y el coeficiente intelectual.

Maple Syrup Urine Disease (MSUD) is caused by a deficiency of the enzyme complex of a-cetoacids dehydrogenases with the consequent accumulation of valine, isoleucine and leucine (VIL) and their metabolites associated with neurotoxicity. It is an autosomal recessive inherited disease and the incidence varies between 1:290.000 and 1:200 newborns. The most frequent presentation is during the neonatal period beginning at the 5th day of life with food refusal, somnolence and coma. If not diagnosed and treated, the patient dies. The treatment when the patient decompensate consists in intensive nutritional therapy to prevent catabolism and reduce leucine levels below 200 µM/L. During the chronic period a VIL- restricted diet is prescribed, supplementing with formula free of VIL, L-valine, L-isoleucine and thiamine. Different studies have demonstrated a strict correlation between age at diagnosis, long-term metabolic control and intellectual quotient.

Molecular and biochemical basis of intermediate maple syrup urine disease. Occurrence of homozygous G245R and F364C mutations at the E1 alpha locus of Hispanic-Mexican patients.

Maple syrup urine disease (MSUD) is caused by a deficiency of the mitochondrial branched-chain alpha-keta acid dehydrogenase (BCKAD) complex. The multienzyme complex comprises five enzyme components, including the E1 decarboxylase with a heterotetrameric (alpha 2 beta 2) structure. Four unrelated Hispanic-Mexican MSUD patients with the intermediate clinical phenotype were diagnosed 7 to 22 mo after birth during evaluation for developmental delay. Three of the four patients were found homozygous for G to A transition at base 895 (exon 7) of the E1 alpha locus, which changes Gly-245 to Arg (G245R) in that subunit. The remaining patient was homozygous for T to G transversion at base 1,253 in the E1 alpha gene, which converts Phe-364 to Cys (F364C) in the gene product. Transfection studies in E1 alpha-deficient lymphoblasts indicate that both G245R and F364C mutant E1 alpha subunits were unable to significantly reconstitute BCKAD activity. Western blotting showed that both mutant E1 alpha subunits in transfected cells failed to efficiently rescue the normal E1 beta through assembly. The putative assembly defect was confirmed by pulse-chase labeling of E1 subunits in a chaperone-augmented bacterial overexpression system. The kinetics of initial assembly of the G245R E1 alpha subunit with the normal E1 beta was shown to be slower than the normal E1 alpha. No detectable assembly of the F364C E1 alpha with normal E1 beta was observed during the 2 h chase. Small amounts of recombinant mutant E1 proteins were produced after 15 h induction with isopropyl thiogalactoside and exhibited very low or no E1 activity. Our study establishes that G245R and F364C mutations in the E1 alpha subunit disrupt both the E1 heterotetrameric assembly and function of the BCKAD complex. Moreover, the results suggest that the G245R mutant E1 alpha allele may be important in the Hispanic-Mexican population.

Enfermedad de la orina olor a jarabe de arce / Maple syrup urine disease

La enfermedad de la orina olor a jarabe de arce, es una afección metabólica producida por deficiencia en la descarboxilación oxidativa de los quetoácidos provenientes de los aminoácidos ramificados valina, isoleucina y leucina. Los pacientes parecen normales hasta los 5 a 7 días de vida, cuando muestran rechazo a la alimentación, vómitos, olor a jarabe de arce en la orina y la piel y deterioro neurológico progresivo, que lleva rápidamente al coma. Se presentan tres niños con enfermedad de la orina olor a jarabe de arce clásica, leucina >2 000 µmol/1, que fueron diagnosticados a los 10, 20 y 21 días de vida, iniciándose inmediatamente el tratamiento en base a la dieta especial. el seguimiento está basado en evaluaciones clínicas, nutricionales y bioquímicas periódicas, para adecuar los requerimientos nutricionales a la evolución de la enfermedad. La evaluación psicométrica, escala de Bayley, mostró que el coeficiente de desarrollo mental estaba entre 50 y 82, relacionándose éste con la edad de diagnóstico. Actualmente los niños tienen entre 2 y 3 años de edad, se encuentran con dieta restringida en los 3 aminoácidos ramificados. Su control debe ser frecuente para evitar desbalances metabólicos y prevenir daños neurológicos ocasionados por éstos

Practical methods to estimate whole body leucine oxidation in maple syrup urine disease.

We report the comparison of noninvasive methods to estimate whole body leucine oxidation in patients who have maple syrup urine disease. We used both an i.v. and an oral bolus of L-[1-13C]leucine and quantitated 13CO2 in expired air. Both methods differentiated patients with maple syrup urine disease from heterozygous and control subjects. Eight patients, whose disease differed in clinical severity, were selected for study and had a range of impaired values for whole body leucine oxidation. Six h after an i.v. bolus dose of L-[1-13C]-L-leucine, 13CO2 recoveries ranged from 0.8 to 19.7%. Three of the eight patients had significant increases in 13CO2 production after supraphysiologic thiamine therapy. After the oral dose of L-[1-13C]leucine, homozygous affected children produced less 13CO2 than normal, age-matched, childhood controls. In addition, the oxidation of orally administered L-[1-13C]leucine was reduced significantly in adult heterozygotes compared with adult controls. The proportion of whole body leucine oxidation by affected children was comparatively greater than that by their cultured cells, but cellular oxidation correlated significantly with whole body oxidation of leucine among affected patients. We conclude that these simplified analyses of whole body leucine oxidation define the degree of impaired branched-chain alpha-ketoacid dehydrogenase activity in patients with differing types of maple syrup urine disease and distinguish the subpopulation who might benefit from thiamine supplementation.

Intermittent neurological symptoms in a girl with a maple syrup urine disease (MSUD) variant.

Severe neurological symptoms, including intermittent ataxia, hallucinations and convulsions, associated with metabolic acidosis and branched-chain amino-acidemia occurred in a six-year-old girl with a variant form of maple syrup urine disease. The symptoms only appeared during periods of infection. Between these periods the girl was healthy and the biochemical findings were normal. In later episodes of infection the condition was successfully treated with a low protein diet and sodium bicarbonate. Analyses of 1-14C-leucine decarboxylase in fibroblasts revealed 10 per cent of normal activity in the girl and 50-70 per cent in the parents. The importance of early diagnosis of MSUD variants is discussed. This is the first published Swedish case of MSUD variant.

Variant maple syrup urine disease in mother and daughter.

Intermittent MSUD in a mother and her daughter is reported. Fibroblast cultures were studied for branched-chain keto acid decarboxylase and results show that the mother has approximately 12% while the daughter has 5% of the normal enzyme activity. Other key members in the family were also studied for enzyme activity. It appears that the child has inherited an abnormal gene from her homozygous mother and another abnormal gene from her heterozygous father.A classification based on the degree of residual enzyme activity and protein tolerance places the mother in grade III and the daughter in grade II category. Classical MSUD, where the enzyme activity is less than 2% of normal, belongs to grade I.