The disorder is transmitted in an autosomal recessive manner. Molecular genetic prenatal diagnosis is also possible when the mutations segregating in the family are known. Antenatal diagnosisĪntenatal diagnosis is possible by measurement of methylmalonate in amniotic fluid and maternal urine at mid-trimester and by studies of functional mutase activity and cobalamin metabolism in cultured amniotic fluid cells. Complementation analysis can be used to identify the cbl or mut complement involved. Differential diagnosisÄifferential diagnoses include methylmalonic acidemia with homocystinuria (see this term), caused by defects in cblC, cblD and cblF, which can be differentiated by the presence of megaloblastic anemia, or vitamin B12-responsive methylmalonic acidemia without homocystinuria (see this term), which usually presents slightly later in life (1 month to 1 year). Diagnosis can be confirmed by somatic cell studies or molecular genetic testing. There is increased propionylcarnitine and/or increased propionylcarnitine-to-acetylcarnitine ratio in dried blood spots by tandem mass spectrometry (MS/MS). Diagnostic methodsÄiagnosis is based on the finding of increased methylmalonic acid in blood and urine. This deficiency is caused by mutations in the MUT gene (6p21). Vitamin B12-unresponsive methylmalonic acidemia without homocystinuria is caused by complete ( mut0) or partial ( mut-) deficiency in the activity of the mitochondrial enzyme methylmalonyl-CoA mutase. These complications are more frequent in mut0 than in mut. Long term consequences are neurological damage due to metabolic stroke and end-stage renal failure. Later-onset and milder phenotypes have also been observed, particularly in mut- patients. They may also have potentially life-threatening ketoacidosis and/or hyperammonemia, renal and neurological complications, metabolic stroke and cardiomyopathy. Patients may also show signs of anemia which is not megaloblastic. Later-onset manifestations may include developmental delay and intellectual deficit. Patients with vitamin B12-unresponsive methylmalonic acidemia without homocystinuria typically present very early in life (<1 to 4 weeks) with features including lethargy, failure to thrive, recurrent vomiting, dehydration, respiratory distress, muscular hypotonia, hepatomegaly and coma. About 25 per cent of all energy from nutrients is utilized by the body to carry on its normal function the remainder becomes heat.Prevalence of 1/48,000-1/61,000 has been reported for methylmalonic aciduria of all causes in North America, and 1/26,000 in China, but only a subset of this is vitamin B12-unresponsive methylmalonic acidemia. Metabolic rate usually is expressed in terms of the amount of heat liberated during the chemical reactions of metabolism. The basal metabolic rate refers to the lowest rate obtained while an individual is at complete physical and mental rest. The rate of metabolism can be increased by exercise by elevated body temperature, as in a high fever, which can more than double the metabolic rate by hormonal activity, such as that of thyroxine, insulin, and epinephrine and by specific dynamic action that occurs following the ingestion of a meal. In the catabolic, or destructive, phase these organized substances are reconverted into simpler compounds, with the release of energy necessary for the proper functioning of the body cells. The anabolic, or constructive, phase is concerned with the conversion of simpler compounds derived from the nutrients into living, organized substances that the body cells can use. There are two phases of metabolism: the anabolic and the catabolic phases. Essentially these processes are concerned with the disposition of the nutrients absorbed into the blood following digestion. the sum of the physical and chemical processes by which living organized substance is built up and maintained ( anabolism), and by which large molecules are broken down into smaller molecules to make energy available to the organism ( catabolism).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |