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Definition:
Metachromatic leukodystrophy (MLD) is the most common form of a family of genetic diseases known as the leukodystrophies. This disorder, also known as Arylsulfatase A deficiency, affects the central and peripheral nervous systems and leads to the breakdown of the nerve’s protective myelin sheath and brain cells. The myelin sheath is a fatty covering that protects nerve fibers. Without it, the nerves in the brain cannot function properly. MLD is caused by a lack of the arylsulfatase A enzyme. Without this enzyme, lipids accumulate in the cells of the nervous system, liver, and kidneys. This accumulation of lipids eventually destroys the myelin sheath. There are three forms of MLD: late infantile, juvenile, and adult. The late infantile form is the most common of the three. Commonly, children affected with MLD are misdiagnosed initially. Misdiagnoses among affected adults include a variety of psychological conditions since the disease first manifests with psychological symptoms. Symptoms:
Children with late-infantile MLD begin showing symptoms just after age one. It is then that they begin to experience difficulty walking. Symptoms include developmental delays, muscle wasting, weakness, and stiffness, a progressive loss of vision which eventually leads to blindness, and swallowing difficulties. Seizures, paralysis, and dementia can also occur. Symptoms for the juvenile form of MLD occur between three and 10 years of age. Symptoms first manifest in impaired school performance, mental deterioration and dementia before symptoms associated with the late-infantile form begin to develop. The late infantile form progresses at a slower rate. The adult form commonly begins after age 16 as a psychiatric disorder or as progressive dementia. The progression of the disorder is slower in the adult form than it is in the other two forms, but its pattern is similar. Inheritance Pattern:
MLD is an autosomal recessive disorder. Diagnosis and Testing:
A diagnosis can be confirmed by measuring the levels of the enzyme, arylsulfatase A, activity in the blood. If low levels of the enzyme are found, a urine test is performed to confirm the presence of sulfatides, a class of lipids. A CT scan or an MRI of the brain may reveal demyelination, or the loss of the myelin sheath. Electrophysiological tests can be performed on various limbs to detect decreased nerve conduction. Genetic screening can determine a diagnosis and/or whether a family member is a carrier. Life Expectancy:
Life expectancy for late infantile MLD is five years of age or younger. Life expectancy for juvenile form of MLD is between 10 and 15 years, following a diagnosis. Treatment:
There is no cure for MLD. Bone marrow or stem cell transplantation may be performed to delay the disorder's progression in some cases, but will not reverse the damage that the brain has endured. These procedures are therefore more successful when MLD is caught before there has been damage to the brain.
Other treatments are supportive and palliative, helping to lessen some of the symptoms associated with this disorder. For example, physical therapy can improve the muscular weakness and stiffening that occurs with this disorder, and medication can control seizure episodes, reduce muscle pain and/or lessen psychological conditions. Assistive devices such as feeding tubes may ensure that nutrition is being maintained. Should muscle deformities lead to a loss of function of a particular joint, surgery may alleviate the contracture. Patient Groups:
Adrenoleukodystrophy Foundation
9906 South Maplewood Avenue
Tulsa, OK 74137
www.aldfoundation.org
Ph: (918)298-8542
David A. Cry, President
davidcry@aldfoundation.org Hunter’s Hope Foundation
P.O. Box 643
Orchard Park, NY 14127
www.huntershope.org
tel: (877) 984-4673
fax: (716) 667-1212
Jim Kelly
info@huntershope.org MLD Foundation (Metachromatic Leukodystrophy)
21345 Miles Drive
West Linn, OR 97068
www.mldfoundation.org
tel: (800) 617-8387
fax: (503) 212-0159
Dean Suhr, President
deansuhr@mldfoundation.org United Leukodystrophy Foundation
2304 Highland Drive
Sycamore, IL 60178
www.ulf.org
tel: (800) 728-5483
fax: (815) 895-2432
Timothy R. Brazeal, Executive Director
office@ulf.org
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