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.

A 1999 retrospective study of 74 cases of neonatal onset found that 32 (43%) patients died during their first hyperammonemic episode. Of those who survived, less than 20% survived to age 14. Few of these patients received liver transplants.

Based on the results of worldwide screening of biotinidase deficiency in 1991, the incidence of the disorder is:

5 in 137,401 for profound biotinidase deficiency

- One in 109,921 for partial biotinidase deficiency

- One in 61,067 for the combined incidence of profound and partial biotinidase deficiency

- Carrier frequency in the general population is approximately one in 120.

This condition is very rare; approximately 600 cases have been reported worldwide. In most parts of the world, only 1% to 2% of all infants with high phenylalanine levels have this disorder. In Taiwan, about 30% of newborns with elevated levels of phenylalanine have a deficiency of THB.

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.

This disorder, epidemiologically speaking, is thought to affect approximately 1 in 50,000 newborns according to Jethva, et al. While in the U.S. state of California there seems to be a ratio of 1 in 35,000.

Raw eggs should be avoided in those with biotin deficiency, because egg whites contain high levels of the anti-nutrient avidin. The name avidin literally means that this protein has an "avidity" (Latin: "to eagerly long for") for biotin. Avidin binds irreversibly to biotin and this compound is then excreted in the urine.

The life expectancy of patients with homocystinuria is reduced only if untreated. It is known that before the age of 30, almost one quarter of patients die as a result of thrombotic complications (e.g., heart attack).

Current research suggests that nearly 8% of the population has at least partial DPD deficiency. A diagnostics determination test for DPD deficiency is available and it is expected that with a potential 500,000 people in North America using 5-FU this form of testing will increase. The whole genetic events affecting the DPYD gene and possibly impacting on its function are far from being elucidated, and epigenetic regulations could probably play a major role in DPD deficiency. It seems that the actual incidence of DPD deficiency remains to be understood because it could depend on the very technique used to detect it. Screening for genetic polymorphisms affecting the "DPYD" gene usually identify less than 5% of patients bearing critical mutations, whereas functional studies suggest that up to 20% of patients could actually show various levels of DPD deficiency.

Women could be more at risk than men. It is more common among African-Americans than it is among Caucasians.

Citrullinemia type I (CTLN1), also known as arginosuccinate synthetase deficiency, is a rare disease caused by a deficiency in argininosuccinate synthetase, an enzyme involved in excreting excess nitrogen from the body. There are mild and severe forms of the disease, which is one of the urea cycle disorders.

The term fatty acid oxidation disorder (FAOD) is sometimes used, especially when there is an emphasis on the oxidation of the fatty acid.

In addition to the fetal complications, they can also cause complications for the mother during pregnancy.

Examples include:

- trifunctional protein deficiency

- MCADD, LCHADD, and VLCADD

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.

Carbamoyl phosphate synthetase I deficiency (CPS I deficiency) is an autosomal recessive metabolic disorder that causes ammonia to accumulate in the blood due to a lack of the enzyme carbamoyl phosphate synthetase I. Ammonia, which is formed when proteins are broken down in the body, is toxic if the levels become too high. The nervous system is especially sensitive to the effects of excess ammonia.

Arginosuccinate synthetase is an enzyme in the urea cycle, which removes excess ammonia from the body. When it is deficient, either fully or partially, ammonia can build up and cause the signs and symptoms of CTLN1.

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.

Short-chain acyl-coenzyme A dehydrogenase deficiency (SCADD), also called ACADS deficiency and SCAD deficiency, is an autosomal recessive fatty acid oxidation disorder which affects enzymes required to break down a certain group of fats called short chain fatty acids.

This condition is inherited in an autosomal recessive pattern, which means two copies of a specific gene in each cell are altered in order for the individual to be afflicted. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

Canine phosphofructokinase deficiency is found mostly in English Springer Spaniels and American Cocker Spaniels, but has also been reported in Whippets and Wachtelhunds. Mixed-breed dogs descended from any of these breeds are also at risk to inherit PFK deficiency.

The signs and symptoms of this disorder typically appear in early childhood. Almost all affected children have delayed development. Additional signs and symptoms can include weak muscle tone (hypotonia), seizures, diarrhea, vomiting, and low blood sugar (hypoglycemia). A heart condition called cardiomyopathy, which weakens and enlarges the heart muscle, is another common feature of malonyl-CoA decarboxylase deficiency.

Some common symptoms in Malonyl-CoA decarboxylase deficiency, such as cardiomyopathy and metabolic acidosis, are triggered by the high concentrations of Malonyl-CoA in the cytoplasm. High level of Malonyl-CoA will inhibits β-oxidation of fatty acids through deactivating the carrier of fatty acyl group, CPT1, and thus, blocking fatty acids from going into the mitochondrial matrix for oxidation.

A research conducted in Netherlands has suggested that carnitine supplements and a low fat diet may help to reduce the level of malonic acid in our body.

Depending on clinical status and the blood ammonia level, the logical first step is to reduce protein intake and to attempt to maintain energy intake. Initiate intravenous infusion of 10% glucose (or higher, if administered through a central line) and lipids.

Intravenous sodium benzoate and sodium phenylacetate may be helpful. Arginine is usually administered with benzoate and phenylacetate. This is best administered in the setting of a major medical center where facilities for hemodialysis in infants is available.

Glycerol phenylbutyrate is a pre-prodrug that undergoes metabolism to form phenylacetate. Results of a phase 3 study comparing ammonia control in adults showed glycerol phenylbutyrate was noninferior to sodium phenylbutyrate. In a separate study involving young children ages 2 months through 5 years, glycerol phenylbutyrate resulted in a more evenly distributed urinary output of PAGN over 24 hours and accounted for fewer symptoms from accumulation of phenylacetate.

In patients with an extremely high blood ammonia level, rapid treatment with hemodialysis is indicated.

Metabolic disease specialists should provide long-term care with very close and frequent follow-up.

Transaldolase deficiency is recognized as a rare inherited pleiotropic metabolic disorder first recognized and described in 2001 that is autosomal recessive. There have been only a few cases that have been noted, as of 2012 there have been 9 patients recognized with this disease and one fetus.

Management for mitochondrial trifunctional protein deficiency entails the following:

- Avoiding factors that might precipitate condition

- Glucose

- Low fat/high carbohydrate nutrition

The treatment goal for individuals affected with OTC deficiency is the avoidance of hyperammonemia. This can be accomplished through a strictly controlled low-protein diet, as well as preventative treatment with nitrogen scavenging agents such as sodium benzoate. The goal is to minimize the nitrogen intake while allowing waste nitrogen to be excreted by alternate pathways. Arginine is typically supplemented as well, in an effort to improve the overall function of the urea cycle. If a hyperammonemic episode occurs, the aim of treatment is to reduce the individual's ammonia levels as soon as possible. In extreme cases, this can involve hemodialysis.

Gene therapy had been considered a possibility for curative treatment for OTC deficiency, and clinical trials were taking place at the University of Pennsylvania in the late 1990s. These were halted after the death of Jesse Gelsinger, a young man taking part in a phase I trial using an adenovirus vector. Currently, the only option for curing OTC deficiency is a liver transplant, which restores normal enzyme activity. A 2005 review of 51 patients with OTC deficiency who underwent liver transplant estimated 5-year survival rates of greater than 90%. Severe cases of OTC deficiency are typically evaluated for liver transplant by 6 months of age.

PNP-deficiency is extremely rare. Only 33 patients with the disorder in the United States have been documented. In the United Kingdom only one child has been diagnosed with this disorder.

Incomplete list of various fatty-acid metabolism disorders.

- Carnitine Transport Defect

- Carnitine-Acylcarnitine Translocase (CACT) Deficiency

- Carnitine Palmitoyl Transferase I & II (CPT I & II) Deficiency

- 2,4 Dienoyl-CoA Reductase Deficiency

- Electron Transfer Flavoprotein (ETF) Dehydrogenase Deficiency (GAII & MADD)

- 3-Hydroxy-3 Methylglutaryl-CoA Lyase (HMG) Deficiency

- Very long-chain acyl-coenzyme A dehydrogenase deficiency (VLCAD deficiency)

- Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHAD deficiency)

- Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCAD deficiency)

- Short-chain acyl-coenzyme A dehydrogenase deficiency (SCAD deficiency)

- 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (M/SCHAD deficiency)