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HEREDITARY MONOGENIC DISEASES

           

Canavan Disease

Canavan disease is a hereditary illness that affects the breakdown and use (metabolism) of aspartic acid. The lack of the aspartoacylase enzyme leads to an accumulation of a material called N-acetylaspartic acid (NAA) in the brain which will cause the white material of the brain to deteriorate.

Canavan disease is a leukodystrophy is a rare disease that results in the progressive decline of the myelin, or “”white matter,”” of the brain.Myelin works by isolating and protecting the axons that send signals from the brain to the rest of the body. Leukodystrophy is caused by genetic defects that lead to an imperfect growth or development of the myelin layer that covers the axon, a part of the nerve cell.

SIGNS AND SYMPTOMS

Clinically, there are two forms of Canavan Disease:

  • Mild Canavan Disease – diagnosed in children; there can be a slight developmental delay, speech problems or problems achieving milestones at school. The NAA level in urine is slightly elevated.
  • Severe Canavan Disease – appears in the neonatal or infancy period; the patients have serious hypotonia (low muscle tone), developmental delay and other neurologic alterations. There are also high NAA concentrations in the blood, urine and cerebrospinal fluid.

Although death often occurs before the patient is 18 months old, some children live to adolescence or, even more rarely, to early adulthood.

Generally, the symptoms begin to appear in the first year of life. The parents notice when the child is not reaching certain fundamental milestones of development such as a lack of head control (head lag), increasing head size (macrocephaly), hytonia (low muscle tone), difficulty swallowing and consequently, feeding problems, seizures, progressive loss of vision and severe mental retardation.

RISK FACTORS

As Canavan disease is hereditary and transmitted from parents to children, the principal risk factor is to have an affected family member. It is more common among the Ashkenazi Jewish population than in the general population.

PREVENTION

Genetic counseling is recommended for people who want to have children and have a family history of Canavan disease. Counseling should be considered if both parents are of Ashkenazi Jewish descent. A diagnosis may be made before the baby is born (prenatal diagnosis) by testing the amniotic fluid

GENE OR REGION STUDIED


  • ASPA
  • SPATA22