Congenital disorder of glycosylation type Ic (Congenital disorder of glycosylation type Ic) - Gen ALG6.
Congenital disorder of glycosylation type Ic (ALG6-CDG) is an inherited disease that affects many parts of the body. Signs and symptoms of the disease vary widely among affected individuals. Individuals with ALG6-CDG usually develop signs and symptoms of the disease during childhood include growth retardation, developmental delay and hypotonia. In addition, affected individuals may have seizures, ataxia, stroke - like episodes involving temporary lethargy and paralysis. In addition, they may develop blood clotting disorders. Some individuals with ALG6-CDG have ocular abnormalities such as strabismus and retinitis pigmentosa, which causes loss of vision. ALG6 women with hypogonadotropic hypogonadism have-CDG, affecting coding hormones that direct sexual development. As a result, these women do not go through puberty.
This process is due to mutations in the gene ALG6, located on the short arm of chromosome 1 (1p31.3). This gene encodes an enzyme involved in glycosylation, a process by which monosaccharides and oligosaccharides to proteins and lipids added. Glycosylation modifies proteins and fats so they can make a greater variety of functions. The enzyme encoded from ALG6 gene transfer glucose oligosaccharide growth. Once the correct number of glucose molecules are linked together, the oligosaccharide binds to a protein or a lipid.
They have identified at least 20 ALG6 gene mutations in people with congenital altered glycosylation type Ic. Mutations in the gene give rise to encoding an enzyme with reduced activity or no activity. A common mutation replaces the amino acid alanine with valine at amino acid position 333 in the enzyme (Ala333Val or A333V), which results in an enzyme with reduced activity. Without a properly functioning enzyme, glycosylation can not proceed normally and oligosaccharides are incomplete. As a result, the glycosylation is reduced or not is performed. The wide variety of signs and symptoms likely due to altered glycosylation of proteins and fats that are necessary for the normal function of many organs and tissues, including the brain, eyes and endocrine system.
This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with congenital altered glycosylation type Ic, by the complete PCR amplification of exons ALG6 gene, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).