Lysosomal storage diseases

Fabry disease is caused by the lack of or faulty enzyme needed to metabolize lipids, fat-like substances that include oils, waxes, and fatty acids. The enzyme is known as ceramide trihexosidase, also called alpha-galactosidase-A. A mutation in the gene that controls this enzyme causes insufficient breakdown of lipids, which build up to harmful levels in the eyes, kidneys, autonomic nervous system, and cardiovascular system. Since the gene that is altered is carried on a mother’s X chromosome, her sons have a 50 percent chance of inheriting the disorder and her daughters have a 50 percent chance of being a carrier. Some women who carry the genetic mutation may have symptoms of the disease. Symptoms usually begin during childhood or adolescence and include burning sensations in the hands that gets worse with exercise and hot weather and small, raised reddish-purple blemishes on the skin. Some boys will also have eye manifestations, especially cloudiness of the cornea. Lipid storage may lead to impaired arterial circulation and increased risk of heart attack or stroke. The heart may also become enlarged and the kidneys may become progressively involved. Other symptoms include decreased sweating, fever, and gastrointestinal difficulties, particularly after eating. Fabry disease is one of several lipid storage disorders.

What is Krabbe Disease?
Krabbé disease is a rare, inherited degenerative disorder of the central and peripheral nervous systems. It is characterized by the presence of globoid cells (cells that have more than one nucleus), the breakdown of the nerve’s protective myelin coating, and destruction of brain cells. Krabbé disease is one of a group of genetic disorders called the leukodystrophies. These disorders impair the growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fibers, and cause severe degeneration of mental and motor skills. Myelin, which lends its color to the “white matter” of the brain, is a complex substance made up of at least 10 different enzymes. Each of the leukodystrophies affects one (and only one) of these substances. Krabbé disease is caused by a deficiency of galactocerebrosidase, an essential enzyme for myelin metabolism. The disease most often affects infants, with onset before age 6 months, but can occur in adolescence or adulthood. Symptoms include irritability, unexplained fever, limb stiffness, seizures, feeding difficulties, vomiting, and slowing of mental and motor development. Other symptoms include muscle weakness, spasticity, deafness, and blindness.

What is Metachromatic Leukodystrophy?

Metachromatic leukodystrophy (MLD) is one of a group of genetic disorders called the leukodystrophies. These diseases impair the growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fibers. Myelin, which lends its color to the white matter of the brain, is a complex substance made up of at least 10 different enzymes. The leukodystrophies are caused by genetic defects in how myelin produces or metabolizes these enzymes. Each of the leukodystrophies is the result of a defect in the gene that controls one (and only one) of the enzymes. MLD is caused by a deficiency of the enzyme arylsulfatase A. MLD is one of several lipid storage diseases, which result in the toxic buildup of fatty materials (lipids) in cells in the nervous system, liver, and kidneys. There are three forms of MLD: late infantile, juvenile, and adult. In the late infantile form, which is the most common MLD, affected children have difficulty walking after the first year of life. Symptoms include muscle wasting and weakness, muscle rigidity, developmental delays, progressive loss of vision leading to blindness, convulsions, impaired swallowing, paralysis, and dementia. Children may become comatose. Most children with this form of MLD die by age 5. Children with the juvenile form of MLD (between 3-10 years of age) usually begin with impaired school performance, mental deterioration, and dementia and then develop symptoms similar to the infantile form but with slower progression. The adult form commonly begins after age 16 as a psychiatric disorder or progressive dementia. Adult-onset MLD progresses more slowly than the infantile form.