NEUROMETABOLIC DISORDERS

Neurometabolic disorders are a group of conditions characterized by issues with brain function and metabolism, or the process by which the body converts food into energy.

• Metachromatic Leukodystrophy (MLD)
  Metachromatic leukodystrophy (MLD) is a rare and life-threatening inherited disease of the body’s metabolic system. MLD is caused by a mutation in the arylsulfatase-A (ARSA) gene that results in the accumulation of fats called sulfatides in the brain and other areas of the body, including the liver, the gallbladder and kidneys. Over time, the nervous system is damaged and children with MLD experience neurological problems such as motor, behavioral and cognitive regression, severe spasticity and seizures, finding it increasingly difficult to move, talk, swallow, eat and see. An estimated 50 percent of children with the most aggressive form of MLD die within five years of disease onset. MLD is estimated to occur in approximately one in every 100,000 live births.
  
  Sources: Mahmood et al. Metachromatic Leukodystrophy: A Case of Triplets with the Late Infantile Variant and a Systematic Review of the Literature. Journal of Child Neurology 2010; Kehrer et al. The natural course of gross motor deterioration in metachromatic leukodystrophy. Dev Med Child Neurol. 2011.

  Cause:
  A genetic mutation that results in the buildup of fats called sulfatides

  Symptoms:
  Loss of sensory, motor and cognitive function

  Impact:
  An estimated half of children with the most aggressive form of MLD die within five years of disease onset

• Mucopolysaccharidosis type I (MPS-I)
  Mucopolysaccharidosis type I (MPS-I) is a rare, inherited neurometabolic disease caused by a deficiency of the alpha-L-iduronidase (IDUA) lysosomal enzyme, which is required to break down sugar molecules called glycosaminoglycans (also known as GAGs). The accumulation of GAGs across multiple organ systems results in symptoms including neurocognitive impairment, skeletal deformity, loss of vision and hearing, and cardiovascular and pulmonary complications. MPS-I occurs at an overall estimated frequency of one in every 100,000 live births. There are three subtypes of MPS-I; approximately 60 percent of children born with MPS-I have the most severe subtype, called Hurler syndrome, and rarely live past the age of 10 when untreated.
  
  Sources: Beck et al. The Natural History of MPS I: Global Perspectives from the MPS I Registry. Genetics in Medicine 2014, 16(10), 759.; Beck et al. The Natural History of MPS I: Global Perspectives from the MPS I Registry. Genetics in Medicine 2014, 16(10), 759.

  Cause:
  A genetic mutation that results in the accumulation of complex carbohydrates called glycosaminoglycans

  Symptoms:
  Neurological, skeletal and cardiovascular problems

  Impact:
  Children born with the most severe form of MPS-I typically die by the age of 10

• Mucopolysaccharidosis type IIIA (MPS-IIIA)
  Mucopolysaccharidosis type IIIA (MPS-IIIA, also known as Sanfilippo syndrome type A) is a rare and life-threatening metabolic disease. People with MPS-IIIA are born with a mutation in the N-sulphoglucosamine sulphohydrolase (SGSH) gene, which, when healthy, helps the body break down sugar molecules called mucopolysaccharides. The buildup of mucopolysaccharides in the brain and other tissues leads to intellectual disability and loss of motor function. MPS-IIIA occurs in approximately one in every 100,000 live births. Life expectancy of children born with MPS-IIIA is estimated to be 10-25 years.
  
  Source: Lavery, C., Hendriksz, C.J. & Jones, S.A. Mortality in patients with Sanfilippo syndrome. Orphanet J Rare Dis 12, 168 (2017) doi:10.1186/s13023-017-0717-y

  Cause:
  A genetic mutation that results in the buildup of sugar molecules called mucopolysaccharides

  Symptoms:
  Progressive intellectual disability and loss of motor function

  Impact:
  Children born with MPS-IIIA rarely live into late-adulthood