Sanfilippo syndrome

Sanfilippo syndrome is a group of inherited lysosomal storage disorders in which impaired heparan sulfate breakdown causes progressive neurological damage.

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Heparan sulfate: A sulfated sugar chain found on cell surfaces and in the extracellular matrix. Its incomplete breakdown is the defining biochemical defect in Sanfilippo syndrome.
Mucopolysaccharidosis: A group of lysosomal disorders involving impaired degradation of glycosaminoglycans. Sanfilippo syndrome is mucopolysaccharidosis type III.
Sanfilippo syndrome type A: The subtype caused by deficient sulfamidase activity, usually resulting from pathogenic variants in SGSH. It is one of the four genetically distinct forms of Sanfilippo syndrome.
Newborn screening: Testing performed shortly after birth to identify conditions before symptoms appear. Screening approaches are being studied to identify Sanfilippo syndrome before neurological decline.
Lysosome: A membrane-bound cell compartment that digests and recycles biological molecules. The enzymes that fail in Sanfilippo syndrome normally work inside lysosomes.
Glycosaminoglycan: A long, unbranched carbohydrate chain made of repeating sugar units. Heparan sulfate is a glycosaminoglycan that accumulates in the syndrome.
Sanfilippo syndrome type B: The subtype caused by deficient alpha-N-acetylglucosaminidase activity, usually resulting from pathogenic variants in NAGLU. It is distinguished from type A by the affected enzyme and gene.
Genetic testing: Analysis of DNA to identify variants associated with inherited conditions. Testing can confirm the subtype by finding pathogenic variants in the relevant gene.
Lysosomal storage disease: An inherited disorder in which defective lysosomal function causes substances to accumulate in cells. Sanfilippo syndrome belongs to this broader group of disorders.
Heparanase: An enzyme that cleaves heparan sulfate chains. Its activity helps explain heparan sulfate turnover, though it is not the defective enzyme in the four Sanfilippo subtypes.