What Is the Life Expectancy of Someone With Sanfilippo Syndrome?

Sanfilippo syndrome is an inherited metabolic disorder caused by a lack of or malfunction of certain enzymes required for the breakdown of glycosaminoglycans molecules. It belongs to the mucopolysaccharidoses group of diseases.

Severe neurological symptoms characterize this condition, which includes:

• Progressive dementia
• Aggressive behavior
• Hyperactivity
• Seizures
• Deafness and loss of vision
• Decreased intellectual functioning (severe mental retardation)
• Inability to sleep for more than a few hours at a time
• Thickened skin
• Mild changes in facial features, bone, and skeletal structures
• Severe diarrhea or constipation
• Liver and spleen enlargement
• Narrowing of the airway passage in the throat
• Enlargement of tonsils and adenoids (difficulty eating and swallowing)
• Recurring respiratory infections

Symptoms of Sanfilippo syndrome

Symptoms typically begin in the toddler years with behavioral issues such as irritability or aggression. Many parents misinterpret these symptoms as autism.

The most serious red flag is when a child begins to lose skills that most children learn as toddlers, such as speech. Sleeping difficulties, coarse facial features, joint stiffness, and abdominal issues are common symptoms.

Sanfilippo syndrome is inherited in an autosomal recessive pattern, which means that the mutated gene must be present in both parents. Parents rarely exhibit symptoms, and they are unlikely to know if they are carriers.

4 types of Sanfilippo syndrome

Sanfilippo syndrome is classified into four types.

Each type is caused by a defect in a different enzyme. Symptoms and progression of these four types of the syndrome differ. The disease typically lasts 8 to 10 years after the onset of symptoms.

1. Sanfilippo A:
   • The most severe type of disorder
   • Caused by missing or altered enzyme heparin N-sulfatase
   • The shortest survival rate among other disorders
2. Sanfilippo B:
   • Caused by missing or altered enzyme alpha-N-acetylglucosaminidase
3. Sanfilippo C:
   • Caused by missing or altered enzyme acetyl-CoA alpha-glucosaminide acetyltransferase
4. Sanfilippo D:
   • Caused by missing or altered enzyme N-acetylglucosamine-6-sulfatase

3 stages of Sanfilippo syndrome

Three stages of Sanfilippo syndrome include:

1. Stage I:
   • Early mental and motor skill development may be delayed
   • Marked decline in learning between the ages of two and six years, followed by eventual loss of language skills and loss of some or all hearing
   • Some children may never learn to speak
   • Difficult to diagnose at this age because children do not appear abnormal
2. Stage II:
   • Typically seen during the ages of 5 to 10 years 
   • Aggressive behavior
   • Hyperactivity
   • Profound dementia
   • Irregular sleep makes the child more difficult to manage
   • Many children chew their hands or anything they can get hold of (a definite safety concern)
3. Stage III:
   • Typically, after the age of 10 years, children become increasingly unsteady on their feet and most are unable to walk by 10 years
   • Growth in height usually stops by 10 years
   • Most children are nonverbal by this stage

Currently, there is no cure for Sanfilippo syndrome, and only supportive or “palliative” care is available.

Participation in a clinical trial is currently the only way for children living with Sanfilippo to try a treatment. Unfortunately, these trials only accept a very small number of patients. Clinical trials are currently underway to assess the safety and efficacy of various approaches. 

Among the potential therapeutic approaches (yet in the research phase only) are

• Gene therapy, in which a harmless virus is used to deliver a functional copy of the altered gene into the body.
• Enzyme replacement therapy involves administering the missing enzyme.
• Substrate reduction therapy, in which researchers are looking for drugs that can reduce the number of mucopolysaccharides the body produces.
• Stem cell therapy, while promising, is still in its early stages of laboratory research.

A child with Sanfilippo syndrome will most likely live between the ages of 15 and 20 years.

Researchers have tried enzyme replacement therapy and bone marrow transplants but these have proven unsuccessful. Gene therapy, chaperone therapy, and intrathecal enzyme therapy are all under investigation.

Couples who want to have children and have a family history of Sanfilippo syndrome should seek genetic counseling.