Definition:
Sialidosis is characterized by a deficiency of the digestive enzyme, alpha-neuraminidase. The lack of this enzyme results in an abnormal accumulation of complex carbohydrates known as mucopolysaccharides, and of fatty substances known as mucolipids. Both of these substances accumulate in bodily tissues. There are four types of Sialidosis: Type I, Type II congenital, Type II infantile, and Type II juvenile. Each type of Sialidosis is characterized by the age of onset and by the type of physical and mental manifestations of this disorder. Type I affects both sexes with equal frequency.

Symptoms:
Symptoms for Sialidosis Type I have a variable range of onset, presenting anywhere from eight to 25 years of age. Symptoms may include sudden involuntary muscle contractions, red spots in the eyes, as well as epilepsy, visual problems, and ataxia. Smoking and menstruation may aggravate the involuntary muscle contractions that are associated with this disorder. Over time, vision decreases and the involuntary muscle contractions can interfere with walking.

Symptoms of Sialidosis Type II congenital are either present at birth or appear within the first year of life. Symptoms include red spots in the eyes as well as detiorating vision over time. An enlargemetn of the spleen and liver, sudden involuntary muscle contractions, coarse facial features, skeletal malformations such as hip dislocation, lack of muscle tone and/or mild mental retardation may also occur.

Symptoms of the Type II infantile form of Sialidosis begin within the first year of life. Mental retardation, coarse facial features, skeletal abnormalities, cherry red spots in the eye, renal complications, and/or spleen or liver enlargement may appear.

Symptoms of the Type II juvenile form of Sialidosis begin anywhere from two to 20 years of age. Coarse facial features, sudden involuntary muscle contractions and cherry red spots are among symptoms of this disorder. Unique to this form of the disorder is the appearance of red to purplish growths on the skin.

Inheritance Pattern:
Sialidosis is an autosomal recessive disorder.

Diagnosis and Testing:
Diagnosis of Sialidosis involves a urine test measuring increased levels oligosaccharides, the type of sugar chains in the lysosome that accumulate as a result of the malfunctioning enzyme. A urine test is routinely followed by a blood test or skin biopsy, which will reveal reduced activity of the enzyme alpha- neuraminidase. Prenatal screening is available to examine alpha- neuraminidase activity in the fetus. Genetic testing is also available in combination with these diagnostic tests to look for the mutation that causes Sialidosis.

Life Expectancy:
Early onset forms of Life Sialidosis are associated with death in early childhood. Later onset forms may be compatible with adult survival.

Treatment:
There is no cure for Sialidosis. Treatment is limited to reducing or controlling the symptoms of this disorder by a patient’s neurologists, ophthalmologists and genetic counselors. Neurologists may assist in controling seizures or nervous system complications. An ophthalmologist may monitor vision loss, and physical and occupational therapists offer help in maintaining muscle movement and reducing muscle discomfort.

Patient Groups:
International Society for Mannosidosis & Related Diseases
P.O. Box 328
Dexter, MI 48130
www.mannosidosis.org
tel: (734) 449-8222
fax: (734) 449-2282
Terri Klein, Executive Director
info@ismrd.org