Sanfilippo A Syndrome
Mucopolysaccharidosis (MPS) Type III (Sanfilippo Syndrome) is an autosomal recessive inborn error of metabolism. It is a genetically and clinically heterogenous group of diseases caused by the deficiency of one of four enzymes (defining subtypes A–D) involved in the degradation of heparan sulfate glycosaminoglycan (GAG). The absence of any one of these enzymes results in the accumulation of heparan sulfate in multiple tissues, leading to progressive central nervous system (CNS) degeneration. MPS IIIA arises when sulfamidase (heparan N-sulfatase) enzyme is deficient.
Symptoms
Sanfilippo A Syndrome (MPS IIIA) is characterized by severe, progressive neurodegeneration in most patients with mild somatic disease. Patients have been reported to be normal at birth and develop normally during the first year of life. Developmental delay becomes apparent in early childhood, and children may exhibit behavioral abnormalities (hyperactivity and aggressive behavior), sleep disturbances, and delayed psychomotor and speech development. Somatic features are often mild and variable. Patients may show coarse facial features, mild skeletal dysostosis multiplex, and hepatosplenomegaly. Mental retardation and dementia become obvious over time, and progressive neurologic degeneration occurs. Patients generally die within the second decade of life.
Diagnosis
Patients with Sanfilippo A Syndrome are typically diagnosed within 2-6 years of age. A physical exam may show signs of liver and spleen swelling. An eye exam will show clear corneas, unlike the cloudy corneas seen in persons with Hurler syndrome (MPS I). Neurological testing will reveal signs of seizures and mental retardation. Urine tests will also be performed; persons with Sanfilippo A Syndrome have large amounts of heparan sulfate in the urine.
Incidence
The incidence of MPS III is estimated as 1 in 53,000-66,000 births. MPS IIIA accounts for about 66% of this incidence.
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