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Alpha 1-antitrypsin deficiency
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Nature of the Genetic Difficulty
Mutations in the CTSA gene cause all forms of galactosialidosis. The CTSA gene provides instructions for making a protein called cathepsin A, which is active in cellular compartments called lysosomes. These compartments contain enzymes that digest and recycle materials when they are no longer needed.
People have two copies of all their genes, including the gene for Galactosialidosis (PPCA). One copy is inherited from the mother in the egg, and one from the father in the sperm.
Only when there is a change in the gene code is there a possibility that the disease will occur. For a person to have Galactosialidosis, they must inherit changes in both of their PPCA genes resulting in instructions that do not function properly. This is known as autosomal recessive inheritance.
For a couple to have a child with Galactosialidosis, both parents must have at least one changed copy of the PPCA gene, which they both pass on to their child. Parents do not have control over which genes they pass on to their children.
If a person has one changed copy of the PPCA gene and one normal copy of the PPCA gene, they are said to be a “carrier” of the condition and will not show any symptoms of Galactosialidosis. If two parents are both carriers, they have a 1 in 4 (25%) chance of having a child with Galactosialidosis in each pregnancy.
Basis Facts of Disease
There are three different types of Galactosialidosis.
It is a Lysosomal storage disease where the enzymes used to breakdown oligosaccharides in lysosomes are not functional. Without the proper breakdown of oligosaccharides these chains of sugars build up in the lysosome and the cell cannot operate efficiently.
All forms of Galactosialidosis are extremely rare.
The prognosis for the first and second type of Galactosialidosis is very poor. The average age of death is usually under one year of life. Symptoms are seen from birth. Infants with Galactosialidosis may have skeletal changes, especially involving the spine. Cognitive and motor delay is also present. The presence of telangectasias (dilation of blood vessels, most commonly on the skin) is unique to the early infantile type of Galactosialidosis. Ophthalmology evaluation may show cherry red spots or other eye changes including corneal clouding. Echocardiogram may show cardiomegaly (enlarged heart).
The third type of Galactosialidosis does not usually have symptoms until the age of 16. Common findings include spinal changes, Neurological problems, eye abnormalities such as corneal clouding and vision loss, and Angiokeratomas (superficial blood vessel dilations).
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