Neonatal onset of medium-chain acyl-CoA dehydrogenase deficiency in two siblings

Neonatal hypoglycaemia and withdrawal symptoms after exposure in utero to valproate

AIMS

To define, in a prospective study, the risk of hypoglycaemia-defined as blood glucose concentration < 1.8 mmol/l-in term infants exposed in utero to valproate and to describe the withdrawal symptoms.

METHODS

Twenty epileptic women were treated with valproate only during pregnancy and two were treated with valproate and carbamazepine. In the first trimester, the daily median dose of valproate was 1.0 g (range 0.3-4.2) and in the third trimester 1.2 g (range 0.3-4.8).

RESULTS

Thirteen of the 22 infants became hypoglycaemic. One infant had eight episodes of hypoglycaemia, one had three episodes, two had two episodes, and nine had one episode each. The lowest blood glucose concentration was 1.0 mmol/l. All episodes were asymptomatic. The maternal mean plasma concentration of total valproate during the third trimester correlated negatively with blood glucose concentration one hour after delivery (p < 0.0003) and with the development of hypoglycaemia (p < 0.0001). There was no evidence for hyperinsulinaemia as the cause of hypoglycaemia. Ten infants developed withdrawal symptoms, which correlated positively with the mean dose of valproate in the third trimester and the concentration of the free fraction of valproate in maternal plasma at delivery (p < 0.02).

CONCLUSIONS

Infants exposed to valproate in utero had a significantly elevated risk of hypoglycaemia, and withdrawal symptoms were often observed.

Fatty acid oxidation disorders as primary cause of sudden and unexpected death in infants and young children: an investigation performed on cultured fibroblasts from 79 children who died aged between 0-4 years

BACKGROUND

Disorders of fatty acid metabolism are known to be responsible for cases of sudden and unexpected death in infancy. At least 14 disorders are known at present. 120 cases of sudden infant death syndrome (SIDS) had been examined for a prevalent mutation (G985) causing medium chain acyl CoA dehydrogenase deficiency, which is inherited in an autosomal recessive mode. No over-representation of either homozygous or heterozygous cases was found.

AIMS

To investigate a broader spectrum of fatty acid oxidation disorders in a wider range of sudden deaths in infants and young children.

METHODS

Seventy nine cases of unexpected death in infants and young children younger than 4 years old were examined for a minimum of nine fatty acid oxidation disorders, using the global [9, 10-3H] myristic acid oxidation assay in cultured fibroblasts from achilles tendon biopsies taken at postmortem examination.

RESULTS

Three cases with fatty acid oxidation disorders and two carriers of the G985 mutation were found, all categorized as non-SIDS or borderline SIDS. The global assay used has the advantage of simplicity.

CONCLUSIONS

These results indicate that disorders of fatty acid oxidation play a small but significant role in the cause of unexpected death in infants and young children, and that infants and children dying in this way should be regarded as high risk candidates for metabolic diseases.

Frequency of 985A-to-G mutation in medium-chain acyl-CoA dehydrogenase gene among patients with sudden infant death syndrome, Reye syndrome, severe motor and intellectual disabilities and healthy newborns in Japan

The prevalence of the 985A-to-G mutation in the medium-chain acyl-CoA dehydrogenase (MCAD) gene among Japanese patients with sudden infant death syndrome, Reye syndrome, unknown fatty acid oxidation disorders and severe motor and intellectual disabilities was studied using the PCR/Nco-I method for molecular diagnosis. A frequency study of this common mutation was also conducted on blood samples and left over Guthrie cards from 329 healthy newborns in Japan. Neither heterozygotes nor homozygotes for the 985A-to-G mutation were identified among both patients and controls. The result of the present study accord with previous reports that MCAD deficiency is a common disorder in Caucasians, but quite rare among Japanese. Therefore, newborn mass-screening for MCAD deficiency using this method will not be practical in Japan. However, it still seems necessary to investigate a child with fatty acid oxidation disorder for the presence of MCAD deficiency, using both biochemical and molecular genetic methods.

Prenatal diagnosis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in a family with a previous fatal case of sudden unexpected death in childhood

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a potentially fatal inherited disease with a carrier frequency of approximately 1:100 in most Caucasian populations. The disease is implicated in sudden unexpected death in childhood. A prevalent disease-causing point mutation (A985G) in the MCAD gene has been characterized, thus rendering diagnosis easy in the majority of cases. Since the clinical spectrum of MCAD deficiency ranges from death in the first days of life to an asymptomatic life, there are probably other genetic factors--in addition to MCAD mutations--involved in the expression of the disease. Thus, families who have experienced the death of a child from MCAD deficiency might have an increased risk of a seriously affected subsequent child. In such a family we have therefore performed a prenatal diagnosis on a chorionic villus sample by a highly specific and sensitive polymerase chain reaction (PCR) assay for the G985 mutation. The analysis was positive and resulted in abortion. We verified the diagnosis by direct analysis on blood spots and other tissue material from the aborted fetus and from family members.

A novel mutation in medium chain acyl-CoA dehydrogenase causes sudden neonatal death

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common known genetic disorder of fatty acid oxidation. Most (approximately 80%) cases are homozygous for a single mutation: A to G replacement at nucleotide 985 (A985G). MCAD deficiency typically presents in the second year of life as hypoketotic hypoglycemia associated with fasting and may progress to liver failure, coma, and death. Prompt diagnosis and management may prevent long-term sequelae. MCAD deficiency was verified by analysis of urinary acylglycine and serum acylcarnitine species from two neonates referred for diagnosis. Full-length cDNA and MCAD exon 7 and 11 genomic clones were prepared for sequence analysis. Normal and mutant cDNAs were expressed in bacteria, and enzymatic activity was assayed by the ferricenium hexaflurophosphate method. Four compound heterozygote individuals from two unrelated families with A985G on one allele and a novel G to A mutation at nucleotide 583 (G583A) as the second mutant allele presented with MCAD deficiency in the first week of life. The expressed G583A mutant protein lacks enzymatic activity. This novel mutation, G583A, is associated with severe MCAD deficiency causing hypoglycemia or sudden, unexpected neonatal death. This previously unrecognized phenotype of MCAD deficiency may contribute significantly to preventable infant deaths.

Medium-chain acyl-coenzyme A dehydrogenase deficiency: clinical course in 120 affected children

Medium-chain acyl-coenzyme A dehydrogenase deficiency is an autosomal recessive disorder of beta-oxidation of fatty acids manifested by episodic hypoglycemia, encephalopathy, apnea, and sudden death. Medical data were obtained on 120 patients with medium-chain acyl-coenzyme A dehydrogenase deficiency referred to Duke University Medical Center for biochemical testing. There were 55 male and 65 female subjects ranging from birth to 19 years of age; 118 subjects were white. Twenty-three children (19%) died before the diagnosis was made. Follow-up data were available in the 97 surviving patients for an average of 2.6 years after diagnosis. Psychodevelopmental data were collected on 73 patients older than 2 years of age. Unexpected morbidity included developmental and behavioral disability, chronic muscle weakness, failure to thrive, and cerebral palsy. We conclude that unidentified patients with this disorder have a significant risk of sudden death in early childhood and that survivors have a significant risk of developmental disability and chronic somatic illness.

Neonatal symptoms in medium chain acyl coenzyme A dehydrogenase deficiency

Medium chain acyl coenzyme A dehydrogenase (MCAD) deficiency has not been thought to be associated with significant neonatal symptoms. To determine the validity of this, all known MCAD cases from New South Wales were reassessed. A total of 16 confirmed and three presumed cases has been identified in New South Wales, from 15 families. The casenotes of patients were reviewed, and where possible the mothers interviewed, either directly or by telephone, to obtain information about neonatal events. Six of the 16 confirmed cases had significant neonatal symptoms, with onset from 17 hours to 3 days of age. All required intravenous dextrose and four of the six needed other interventions, including hospital transfer. One baby died. All six were breast fed, but so were five of the eight asymptomatic neonates for whom information was available. Four of the six symptomatic neonates were homozygous for the common MCAD mutation, an A to G transition at position 985, and one was heterozygous. It is concluded that serious neonatal symptoms are common in MCAD. Newborn siblings of MCAD cases must have careful monitoring and support during the first few days of life.