A 1994 study of the entire population of New South Wales (Australia) found 20 patients. Of these, 5 (25%) had died at or before 30 months of age. Of the survivors, 1 (5%) was severely disabled and the remainder had either suffered mild disability or were making normal progress in school. A 2006 Dutch study followed 155 cases and found that 27 individuals (17%) had died at an early age. Of the survivors, 24 (19%) suffered from some degree of disability, of which most were mild. All the 18 patients diagnosed neonatally were alive at the time of the follow-up.

A 2006 study of 279 patients found that of those with symptoms (185, 66%), 95% had suffered an encephalopathic crises usually with following brain damage. Of the persons in the study, 49 children died and the median age of death was 6.6 years. A Kaplan-Meier analysis of the data estimated that about 50% of symptomatic cases would die by the age of 25.

Due to the rarity of the disease, it is hard to estimate mortality rates or life expectancy. One 2003 study which followed 88 cases receiving two different kinds of treatment found that very few persons lived beyond age 20 and none beyond age 30.

Less than 20 patients with MGA type I have been reported in the literature (Mol Genet Metab. 2011 Nov;104(3):410-3. Epub 2011 Jul 26.)

Vegetarian diets and, for younger children, breastfeeding are common ways to limit protein intake without endangering tryptophan transport to the brain.

That MMA can have disastrous effects on the nervous system has been long reported; however, the mechanism by which this occurs has never been determined. Published on June 15th 2015, research performed on the effects of methylmalonic acid on neurons isolated from fetal rats in an in vitro setting using a control group of neurons treated with an alternate acid of similar pH. These tests have suggested that methylmalonic acid causes decreases in cellular size and increase in the rate of cellular apoptosis in a concentration dependent manner with more extreme effects being seen at higher concentrations. Furthermore, micro-array analysis of these treated neurons have also suggested that on a epigenetic-level methylmalonic acid alters the transcription rate of 564 genes, notably including those involved in the apoptosis, p53, and MAPK signaling pathways.

This condition is sometimes mistaken for Reye syndrome, a severe disorder that develops in children while they appear to be recovering from viral infections such as chicken pox or flu. Most cases of Reye syndrome are associated with the use of aspirin during these viral infections.

MCADD is most prevalent in individuals of Northern European Caucasian descent. The incidence in Northern Germany is 1:4000, currently the highest in the world. Northern Europe is also the origin of the common mutation in MCADD. For populations without origins in Northern Europe, the incidence is significantly lower, 1:51,000 in Japan and 1:700,000 in Taiwan. The common mutation has not been identified in MCADD cases identified in Asian populations.

The disorder is caused by a mutation in the "ACADSB" gene, located on the long arm of human chromosome 10 (10q25-q26). It is inherited in an autosomal recessive manner, which means an affected individual must inherit one copy of the mutation from each parent.

Most individuals with SBCADD are identified through newborn screening, where they present with an elevation of a five carbon acylcarnitine species. Confirmatory testing includes plasma and urine analysis to identify the carnitine and glycine conjugates of 2-methylbutyryl-CoA.

Propionic acidemia is inherited in an autosomal recessive pattern and is found in about 1 in 35,000 live births in the United States. The condition appears to be more common in Saudi Arabia, with a frequency of about 1 in 3,000. The condition also appears to be common in Amish, Mennonite and other populations where inbreeding is common.

There is a deficiency of malate in patients because fumarase enzyme can't convert fumarate into it therefore treatment is with oral malic acid which will allow the krebs cycle to continue, and eventually make ATP.

Fumarase deficiency is caused by a mutation in the fumarate hydratase (FH) gene in humans, which encodes the enzyme that converts fumarate to malate in the mitochondria. Other mutant alleles of the FH gene, located on human Chromosome 1 at position 1q42.1, cause multiple cutaneous and uterine leiomyomata, hereditary leiomyomatosis and renal cell cancer. Fumarase deficiency is one of the few known deficiencies of the Krebs cycle or tricarboxylic acid cycle, the main enzymatic pathway of cellular aerobic respiration.

The condition is an autosomal recessive disorder, and it is therefore usually necessary for an affected individual to receive the mutant allele from both parents. A number of children diagnosed with the disorder have been born to parents who were first cousins. It can also be associated with uniparental isodisomy.

Argininosuccinic aciduria occurs in approximately 1 in 70,000 live births. Many patients can now be detected on the newborn screen if their blood citrulline is elevated.

Malonyl-CoA decarboxylase deficiency (MCD), or Malonic aciduria is an autosomal-recessive metabolic disorder caused by a genetic mutation that disrupts the activity of Malonyl-Coa decarboxylase. This enzyme breaks down Malonyl-CoA (a fatty acid precursor and a fatty acid oxidation blocker) into Acetyl-CoA and carbon dioxide.

The inherited forms of methylmalonic acidemia cause defects in the metabolic pathway where methylmalonyl-coenzyme A (CoA) is converted into succinyl-CoA by the enzyme methylmalonyl-CoA mutase.

Vitamin B is also needed for the conversion of methylmalonyl-CoA to Succinyl-CoA. Mutations leading to defects in vitamin B metabolism or in its transport frequently result in the development of methylmalonic acidemia.

This disorder has an autosomal recessive inheritance pattern, which means the defective gene is located on an autosome, and two copies of the gene—one from each parent—must be inherited to be affected by the disorder. The parents of a child with an autosomal recessive disorder are carriers of one copy of the defective gene, but are usually not affected by the disorder.

Without the enzymatic activity of Malonyl-CoA decarboxylase, cellular Mal-CoA increases so dramatically that at the end it is instead broken down by an unspecific short-chain acyl-CoA hydrolase, which produces malonic acid and CoA. Malonic acid is a Krebs cycle inhibitor, preventing the cells to make ATP through oxidation. In this condition, the cells, to make ATP, are forced to increase glycolysis, which produces lactic acid as a by-product. The increase of lactic and malonic acid drastically lowers blood pH, and causes both lactic and malonic aciduria (acidic urine). This condition is very rare, as fewer than 20 cases have been reported.

By 1999, only seven cases of Malonyl- CoA decarboxylase deficiency had been reported in human in Australia; however, this deficiency predominately occurs during childhood. Patients from the seven reported cases of Malonyl- CoA decarboxylase deficiency have an age range between 4 days to 13 years, and they all have the common symptom of delayed neurological development. Similar study was conducted in Netherland, and found seventeen reported cases of Malonyl- CoA decarboxylase deficiency in children age range from 8 days to 12 years.

Although we have not yet gained a clear understanding of the pathogenic mechanism of this deficiency, some researchers have suggested a brain-specific interaction between Malonyl-CoA and CTP1 enzyme which may leads to unexplained symptoms of the MCD deficiency.

Research has found that large amount of MCD are detached in the hypothalamus and cortex of the brain where high levels of lipogenic enzymes are found, indicating that MCD plays a role in lipid synthesis in the brain. Disturbed interaction between Malonyl-CoA and CPT1 may also contributed to abnormal brain development.

Malonyl-CoA decarboxylase plays an important role in the β-oxidation processes in both mitochondria and peroxisome. Some other authors have also hypothesized that it is the MCD deficiency induced inhibition of peroxisomal β-oxidation that contributes to the development delay.

Propionic acidemia, also known as propionic aciduria, propionyl-CoA carboxylase deficiency and ketotic glycinemia, is an autosomal recessive metabolic disorder, classified as a branched-chain organic acidemia.

The disorder presents in the early neonatal period with progressive encephalopathy. Death can occur quickly, due to secondary hyperammonemia, infection, cardiomyopathy, or basal ganglial stroke.

Propionic acidemia is a rare disorder that is inherited from both parents. Being autosomal recessive, neither parent shows symptoms, but both carry a defective gene responsible for this disease. It takes two faulty genes to cause PA, so there is a 1 in 4 chance for these parents to have a child with PA.

In the world less than 1 in 1.00.000 have HIDS [5]. 200 individuals throughout the world do suffer from MVK.

Urocanic aciduria, also called urocanate hydratase deficiency or urocanase deficiency, is an autosomal recessive metabolic disorder caused by a deficiency of the enzyme urocanase. It is a secondary disorder of histidine metabolism.

Urocanic aciduria is thought to be relatively benign. Although aggressive behavior and mental retardation have been reported with the disorder, no definitive neurometabolic connection has yet been established.

Mevalonate kinase deficiency, also called mevalonic aciduria and hyper immunoglobin D syndrome is an autosomal recessive metabolic disorder that disrupts the biosynthesis of cholesterol and isoprenoids.

It is characterized by an elevated level of immunoglobin D in the blood.

The enzyme is involved in biosynthesis of cholesterols and isoprenoids. The enzyme is necessary for the conversion of mevalonate to mevalonate-5-phosphate in the presence of Mg2+ [Harper’s biochemistry manual]. Mevalonate kinase deficiency causes the accumulation of mevalonate in urine and hence the activity of the enzyme is again reduced Mevalonate kinase deficiency. It was first described as HIDS in 1984.

Glutaric acidemia type 2 often appears in infancy as a sudden metabolic crisis, in which acidosis and low blood sugar (hypoglycemia) cause weakness, behavior changes, and vomiting. There may also be enlargement of the liver, heart failure, and a characteristic odor resembling that of sweaty feet. Some infants with glutaric acidemia type 2 have birth defects, including multiple fluid-filled growths in the kidneys (polycystic kidneys). Glutaric acidemia type 2 is a very rare disorder. Its precise incidence is unknown. It has been reported in several different ethnic groups.

3-Methylglutaconic aciduria (MGA) is any of at least five metabolic disorders that impair the body's ability to make energy in the mitochondria. As a result of this impairment, 3-methylglutaconic acid and 3-methylglutaric acid build up and can be detected in the urine.

3-Methylglutaconic acid is an organic acid. The double carboxylic acid functions are the principal cause of the strength of this acid. 3-methylglutaconic acid can be detected by the presence of the acid function and the double connection that involves reactivity with some specific substances.

The treatment of 2-Hydroxyglutaric aciduria is based on seizure control, the prognosis depends on how severe the condition is.