Biomarker for Sanfilippo Disease Type A-B-C-D AN INTERNATIONAL, MULTICENTER, EPIDEMIOLOGICAL PROTOCOL

The Mucopolysaccharidoses (MPS Disorders) are a group of rare genetic disorders caused by the deficiency of one of the lysosomal enzymes, resulting in an inability to metabolize complex carbohydrates (mucopolysaccharides) into simpler molecules. High concentrations of mucopolysaccharides in the cells of the central nervous system, including the brain, cause the neu-rological and developmental deficits that accompany these disorders.

Lysosomal enzymes are found in the lysosome, a very small membrane-contained body (organelle) found in the cytoplasm of most cells. The lysosome is often called the "waste disposal plant" of the cell. The accumulation of these large, undegraded mucopolysaccharides in the cells of the body is the cause of a number of physical symptoms and abnormalities.

MPS-III (Sanfilippo Syndrome) is one of seven MPS Disorders. It is an inborn error of metabolism that is transmitted as an autosomal recessive genetic disorder. MPS-lll has been categorized into four subtypes: MPS-III Type A, MPS-III Type B, MPS-III Type C, and MPS-III Type D depending on the gene defect (MPS3A - SGSH gene, MPS3B - NAGLU gene, MPS3C - HGSNAT, MPS3D - GNS gene). All types are associated with some degree of mental deterioration, but the severity depends on the particular type of MPS-lll. Several physical defects may be present, and the severity of these defects varies with the type of MPS-III. In the case of each type of MPS-III, abnormal amounts of a specific, chemically complex molecule is excreted in the urine. The excreted chemical is the same for each of the four types of MPS-III, since the defective gene involves a different step, and thus a different enzyme, in the deconstruction of the same mucopolysaccharide. By testing for one or another of these enzymes, the variant type may be readily identified.

Symptoms Patients with Sanfilippo Syndrome (MPS Type III) usually appear normal at birth, but mental retardation and developmental delay is usually evident by age 3-5 years. Mental and motor development reaches a peak by 3-6 years of age after which behavioral disturbances and intellectual decline usually occur. However, hyperactivity and irritability may become obvious earlier.

The following symptoms are usually apparent by approximately age 10: neurological deficits and signs, wobbly and erratic gait and difficulty walking (ataxia), hyperactivity (hyperkinetic syndrome), mental retardation, stiff joints, hernias, enlarged liver and/or spleen (hepatosplenomegaly).Growth is usually minimally affected; the head may be enlarged, and abnormal hairiness (hirsutism) may occur. Mild coarsening of facial features also characterizes this disorder. In some cases deafness may also occur.