Sanfilippo syndrome, also known as mucopolysaccharidosis type III (MPS III), is a rare genetic metabolism disorder that primarily affects the brain and spinal cord. It is caused by a lack of an enzyme that normally breaks down and recycles a large, complex sugar molecule called heparan sulphate. This leads to a buildup of large sugar molecules called glycosaminoglycans (GAGs) in the bodys lysosomes, which causes serious problems in the brain and nervous system. Sanfilippo syndrome is classified as a lysosomal storage disorder (LSD) and belongs to a group of diseases called mucopolysaccharidoses (MPSs) . There are four subtypes of Sanfilippo syndrome, each corresponding to a lack of a different enzyme responsible for a different step of breaking down heparan sulphate. Symptoms of Sanfilippo syndrome include developmental delays, behavioral issues, speech problems, respiratory infections, seizures, severe cognitive problems, and progressive loss of motor skills. Sanfilippo syndrome affects life expectancy, and most children with the condition never reach adulthood. There is currently no cure for Sanfilippo syndrome, but doctors and researchers are working hard to find better treatments for it.