World Sanfilippo Awareness Day Date in the current year: November 16, 2025

Sanfilippo syndrome, also known as mucopolysaccharidosis type III (MPS III), is caused by the accumulation of glycosaminoglycans (mucopolysaccharides) in the body. This accumulation is caused by a mutation in one of four genes that encode enzymes responsible for breaking down the polysaccharide heparan sulfate.

There are four types of Sanfilippo syndrome (A, B, C, and D), which depend on which gene is affected. Type A is the most common and severe, types B and C are rarer, and type D is the least common. Sanfilippo syndrome has an autosomal recessive inheritance pattern, meaning a person must inherit two copies of the mutated gene, one from each parent, to develop the disorder. Individuals with one affected copy are carriers who may pass the mutation to their children.

Children with Sanfilippo syndrome do not typically exhibit symptoms immediately after birth, even though the syndrome is already present. Some patients have distinctive facial features, such as a prominent forehead, thick eyebrows, a large nose, and a full lower lip, which are often dismissed.

The first symptoms usually appear between ages one and four. These symptoms include developmental delays, particularly in speech and language, as well as behavioral problems such as hyperactivity, temper tantrums, aggressive or destructive behavior, sleep disturbances, and difficulties with toilet training.

As the disease progresses, more severe symptoms appear. These include progressive intellectual disability, sensorineural hearing loss, a gradual loss of motor skills due to increasing muscle and joint stiffness, seizures, difficulty chewing and swallowing, chronic ear and respiratory infections, and dementia. Over time, patients lose the ability to walk and speak, become bedridden, and ultimately pass away.

Because of its progressive nature and symptoms, Sanfilippo syndrome is sometimes referred to as “childhood dementia” or “childhood Alzheimer’s”. Patients with types A and B usually survive until their late teens. Type C is less aggressive, and some patients with this type may survive into their 30s. Type D is extremely rare, and there is no data on the average life expectancy of patients with this type.

Like most genetic diseases, Sanfilippo syndrome is incurable. Treatments such as gene therapy, enzyme therapy, and substrate reduction therapy are being studied, but none have been approved yet. The current treatment focuses on managing symptoms, maintaining comfort, and improving quality of life.

World Sanfilippo Awareness Day was created to raise global awareness of this rare syndrome, support affected families, and honor those who have passed away from the disease. You can get involved by donating to an organization that supports patients or funds research, helping to raise funds, and spreading the word on social media with the hashtag #WorldSanfilippoDay.