There is currently no therapy or cure for MLD in late infantile patients displaying symptoms, or for juvenile and adult onset with advanced symptoms. These patients typically receive clinical treatment focused on pain and symptom management.

Pre-symptomatic late infantile MLD patients, as well as those with juvenile or adult MLD that are either presymptomatic or displaying mild symptoms, can consider bone marrow transplantation (including stem cell transplantation), which may slow down progression of the disease in the central nervous system. However, results in the peripheral nervous system have been less dramatic, and the long-term results of these therapies have been mixed. Recent success has involved stem cells being taken from the bone marrow of children with the disorder and infecting the cells with a retro-virus, replacing the stem cells' mutated gene with the repaired gene before re-injecting it back into the patient where they multiplied. The children by the age of five were all in good condition and going to kindergarten when normally by this age, children with the disease can not even speak.

Several therapy options are currently being investigated using clinical trials primarily in late infantile patients. These therapies include gene therapy, enzyme replacement therapy (ERT), substrate reduction therapy (SRT), and potentially enzyme enhancement therapy (EET).

A team of international researchers and foundations gathered in 2008 to form an international MLD Registry to create and manage a shared repository of knowledge, including the natural history of MLD. This consortium consisted of scientific, academic and industry resources. This registry never became operational.

With many different types of leukodystrophies and causes, treatment therapies vary for each type. Many studies and clinical trials are in progress to find treatment and therapies for each of the different leukodystrophies. Stem cell transplants and gene therapy appear to be the most promising in treating all leukodystrophies providing it is done as early as possible.

For hypomyelinating leukodystrophies, therapeutic research into cell-based therapies appears promising. Oligodendrocyte precursor cells and neural stem cells have been transplanted successfully and have shown to be healthy a year later. Fractional anisotropy and radial diffusivity maps showed possible myelination in the region of the transplant. Induced pluripotent stem cells, oligodendrocyte precursor cells, gene correction, and transplantation to promote the maturation, survival, and myelination of oligodendrocytes seem to be the primary routes for possible treatments.

For three types of leukodystrophies (X-linked adrenoleukodystrophy (X-ALD), metachromatic leukodystrophy (MLD) and Krabbe Disease (globoid cell leukodystrophy - GLD), gene therapy using autologous hematopoietic stem cells to transfer the disease gene with lentiviral vectors have shown to be successful and are currently being used in clinical trials for X-ALD and MLD. The progression of X-ALD has shown to be disrupted with hematopoietic stem cell gene therapy but the exact reason why demyelination stops and the amount of stem cells needed is unclear. While there is an accumulation of very long chain fatty acids in the brain, it does not seem to be the reason behind the disease as gene therapy does not correct it.

Adeno-associated vectors have also been used in intracerebral injections to treat MLD. In some patients with MLD, their IQ increased, nerve conduction improved, their MRIs appeared stable, and had normal enzyme levels. Although the greater majority of patients seem to improve after the transplant, some do not respond well to treatment, which may cause devastating outcomes. For those leukodystrophies that result from a deficiency of lysozyme enzymes, such as Krabbes disease, enzyme replacement therapy seems hopeful, however, this proves difficult as the blood-brain barrier severely limits what can pass through into the central nervous system. Due to this obstacle, most research and clinical trials are turning to allogeneic hematopoietic stem cell transplantation.

"(current as of January 2017)"

- Shire, with headquarters in Switzerland and a major research center in Lexington, MA, is developing and studying their intrathecal SHP 611 (formerly HGT-1110) ERT [Enzyme Replacement Therapy].

- Clinical Trial

- Recruiting for the clinical trial started January, 2012 and was fully recruited by mid-2014.

- a Fourth cohort was recruited during the first half of 2016. This cohort is fully populated and no new patients are being recruited. Data from this cohort will be gathered by late 2016 with another 3–6 months of outcome analysis expected before a decision is made on what the next drug development and Trial plans will be.

- Phase I/II data is scheduled to be presented in February 2017 at the LDN/WORLD conference.

- Early (post-40 week) results showed the drug was well tolerated at all doses and the 100 mg dose showed the slowest decline in GMFM-88 scores over the trial period. Data continues to be studied.

- Trial Centers

- Trial centers were opened in Europe, South America and Australia

- Patients were successfully recruited in all trial centers

- Inclusion Criteria

- 1st symptoms before age 30 months, currently 7 years old or younger

- Ambulatory – be able to walk 10 steps while holding only one hand.

- Additional clinical trial information & inclusion criteria, can be found on the MLD Foundation website here and at the Clinical Trials.gov site.

- The clinical trial is a 38-week multi-site study of 18 children in three different dosing cohorts. The 'no treatment' placebo arm was removed from the trial in June 2012.

- Patients must go to one of five trial sites for their every other week enzyme infusions: Copenhagen Denmark, Paris France, Tübingen Germany, Sydney Australia, or Porto Alegre Brazil. Derqui, Argentina is awaiting approval.

- A new intrathecal port from a new vendor was approved for use starting December 2013. See the MLD Foundation website for more details.

- SHP611 has "orphan product" status in both Europe and the United States.

- "History:" Shire suspended development of the Metazyme intravenous ERT product in 2010. It was in clinical trial when it was acquired from Zymenex in 2008 (subsequently renamed HGT-1111 by Shire) after it was shown to not have sufficient efficacy by a Phase I/II clinical trial in Europe. The initial study completed September 2008 and the extension study completed October 2010 with the cessation of product supply to trial participants.

MLD Foundation provides updates on MLD research, including (as of 2017) three clinical trials evaluating gene therapy and enzyme replacement therapy, and various lines of basic research. They are also active in newborn screening.

The Global Leukodystrophy Initiative was formed in 2013 to bring together clinicians, researchers and advocacy groups to focus and improve both clinical care and research.

In addition, many research groups are studying the cellular processes of myelination, which may provide insights into leukodystrophy. Researchers in New York have successfully cured leukodystrophy in mice, using skin cells to repair damaged myelin sheaths. Researchers hypothesize that this treatment may possibly be used in curing human multiple sclerosis.

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.

Diagnosis of canine phosphofructokinase deficiency is similar to the blood tests used in diagnosis of humans. Blood tests measuring the total erythrocyte PFK activity are used for definitive diagnosis in most cases. DNA testing for presence of the condition is also available.

Treatment mostly takes the form of supportive care. Owners are advised to keep their dogs out of stressful or exciting situations, avoid high temperature environments and strenuous exercise. It is also important for the owner to be alert for any signs of a hemolytic episode. Dogs carrying the mutated form of the gene should be removed from the breeding population, in order to reduce incidence of the condition.

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.

In terms of treatment for short-chain acyl-CoA dehydrogenase deficiency, some individuals may not need treatment, while others might follow administration of:

- Riboflavin

- Dextrose

- Anticonvulsants

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.

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.

A diagnosis can be made through a muscle biopsy that shows excess glycogen accumulation. Glycogen deposits in the muscle are a result of the interruption of normal glucose breakdown that regulates the breakdown of glycogen. Blood tests are conducted to measure the activity of phosphofructokinase, which would be lower in a patient with this condition. Patients also commonly display elevated levels of creatine kinase.

Treatment usually entails that the patient refrain from strenuous exercise to prevent muscle pain and cramping. Avoiding carbohydrates is also recommended.

A ketogenic diet also improved the symptoms of an infant with PFK deficiency. The logic behind this treatment is that the low-carb high fat diet forces the body to use fatty acids as a primary energy source instead of glucose. This bypasses the enzymatic defect in glycolysis, lessening the impact of the mutated PFKM enzymes. This has not been widely studied enough to prove if it is a viable treatment, but testing is continuing to explore this option.

Genetic testing to determine whether or not a person is a carrier of the mutated gene is also available.

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.

Management for mitochondrial trifunctional protein deficiency entails the following:

- Avoiding factors that might precipitate condition

- Glucose

- Low fat/high carbohydrate nutrition

At this time there is no treatment for transaldolase deficiency.

There is currently research being done to find treatments for transaldolase deficiency. A study done in 2009 used orally administered N-acetylcysteine on transaldolase deficient mice and it prevented the symptoms associated with the disease. N-acetylcysteine is a precursor for reduced glutathione, which is decreased in transaldolase deficient patients.

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.

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.

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).

Purine nucleoside phosphorylase deficiency, often called PNP-deficiency, is a rare autosomal recessive metabolic disorder which results in immunodeficiency.

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.

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.

Treatment of THB deficiencies consists of THB supplementation (2–20 mg/kg per day) or diet to control blood phenylalanine concentration and replacement therapy with neurotransmitters precursors (L-DOPA and 5-HTP) and supplements of folinic acid in DHPR deficiency.

Tetrahydrobiopterin is available as a tablet for oral administration in the form of "tetrahydrobiopterin dihydrochloride" (BH4*2HCL). BH4*2HCL is FDA approved under the trade name Kuvan. The typical cost of treating a patient with Kuvan is $100,000 per year. BioMarin holds the patent for Kuvan until at least 2024, but Par Pharmaceutical has a right to produce a generic version by 2020. BH4*2HCL is indicated at least in tetrahydrobiopterin deficiency caused by GTPCH deficiency or PTPS deficiency.

Low-protein food is recommended for this disorder, which requires food products low in particular types of amino acids (e.g., methionine).

Individuals presenting with Type III galactosemia must consume a lactose- and galactose-restricted diet devoid of dairy products and mucilaginous plants. Dietary restriction is the only current treatment available for GALE deficiency. As glycoprotein and glycolipid metabolism generate endogenous galactose, however, Type III galactosemia may not be resolved solely through dietary restriction.

Enolase Deficiency is a rare genetic disorder of glucose metabolism. Partial deficiencies have been observed in several caucasian families. The deficiency is transmitted through an autosomal dominant inheritance pattern. The gene for Enolase 1 has been localized to Chromosome 1 in humans. Enolase deficiency, like other glycolytic enzyme deficiences, usually manifests in red blood cells as they rely entirely on anaerobic glycolysis. Enolase deficiency is associated with a spherocytic phenotype and can result in hemolytic anemia, which is responsible for the clinical signs of Enolase deficiency.