Pediatrics
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January 7, 2025

Sanfilippo Syndrome: A Comprehensive Guide for Your Family

Written By
Medically Reviewed by
Dr. Sarah Daglis ND
Updated On
January 15, 2025

When your child is diagnosed with a rare condition like Sanfilippo syndrome, it can feel overwhelming. You may have questions about what this condition means, how it might impact your family, and how you can support your child's health and well-being. 

Sanfilippo syndrome is caused by the body's inability to break down specific sugar molecules, which can build up and affect the brain and other organs. Although there is no cure, understanding the condition can help families make informed decisions. 

This article covers the basics of Sanfilippo syndrome, including what it is, how it's diagnosed, the stages of the condition, and strategies for supporting your child and family.

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What is Sanfilippo Syndrome?

Sanfilippo syndrome is a rare genetic disorder that impacts the body's ability to break down and recycle a specific type of sugar molecule called glycosaminoglycans (GAGs), previously known as mucopolysaccharides. It is alternatively known as Mucopolysaccharidosis Type III (MPS III). 

These sugar molecules are essential for building and maintaining healthy tissues in the body. However, in children with Sanfilippo syndrome, mutations in specific genes prevent the body from producing certain enzymes needed to break them down. 

Over time, GAG accumulation leads to gradual damage, significantly affecting the brain, nervous system, and other organ systems.

Classification of Sanfilippo Syndrome: Types A, B, C, and D

Sanfilippo syndrome is further classified into four subtypes based on the specific enzyme deficiency involved:

  1. Type A (SGSH): Caused by a deficiency in the enzyme heparan-N-sulfatase. This is the most severe and common form.
  2. Type B (NAGLU): Caused by a deficiency in the enzyme N-acetyl-α-glucosaminidase.
  3. Type C (HGSNAT): Caused by a deficiency in acetyl-CoA: α-glucosaminide N-acetyltransferase.
  4. Type D (GNS): Caused by a deficiency in N-acetylglucosamine-6-sulfatase. This is the rarest subtype.

While the symptoms and progression of the disease are similar across all subtypes, the specific genetic mutation determines which enzyme is missing.

History of Sanfilippo Syndrome

Sanfilippo syndrome was first described in 1963 by American pediatrician Dr. Sylvester Sanfilippo and his colleagues. Based on its unique symptoms and underlying enzyme deficiencies, they identified the condition as a distinct form of mucopolysaccharidosis. 

Since then, research has advanced our understanding of the condition, but Sanfilippo syndrome remains a challenge for diagnosis and treatment due to its rarity.

Key Statistics on Prevalence

Statistics may vary across studies and regions due to differences in reporting and diagnostic access.

  • Sanfilippo syndrome is considered a rare disease, with an estimated prevalence of 1 in 70,000 births worldwide.
  • It affects children of all ethnic backgrounds, though the frequency of specific subtypes may vary by region.
  • The most worldwide prevalent mucopolysaccharidosis type III (MPS III) subtypes are A and B.

Causes and Risk Factors

Sanfilippo syndrome is caused by genetic mutations that disrupt the body's ability to break down GAGs, leading to their accumulation and progressive cellular damage.

Genetic Basis

Sanfilippo syndrome is linked to mutations in specific genes that produce enzymes needed to break down GAGs. The affected gene determines which enzyme is missing or non-functional, depending on the subtype. 

GAGs cannot be broken down and recycled without these enzymes, leading to their accumulation in cells, particularly in the brain and nervous system.

Sanfilippo syndrome follows an autosomal recessive inheritance pattern, meaning a child must inherit two copies of the mutated gene—one from each parent—to develop the condition. 

Parents with one copy of the mutated gene are considered carriers and usually do not exhibit symptoms.

If both parents are carriers, there is a 25% chance with each pregnancy that their child will inherit the condition, a 50% chance the child will be a carrier, and a 25% chance the child will not inherit a mutation.

Families with a known history of genetic disorders may benefit from consulting a genetic counselor for tailored risk assessment.

Risk Factors

  1. Familial Genetic History: A family history of Sanfilippo syndrome or known carriers of the gene increases the risk of passing the condition on to offspring. Genetic testing can help identify carrier status in at-risk families.
  2. Rare Mutation Probability in General Populations: Although Sanfilippo syndrome is rare, genetic mutation carriers exist in the general population. The likelihood of two carriers having a child together is very low unless there is a familial connection or a high carrier frequency within specific populations.

Symptoms and Progression

Sanfilippo syndrome is a progressive condition, meaning its symptoms worsen over time as the disease affects the brain and other body parts. While symptoms and their progression vary among individuals, the condition commonly includes the following:

Early Symptoms

In the early stages of Sanfilippo syndrome, symptoms often appear subtle and may mimic common childhood challenges, making early diagnosis difficult. These early signs typically emerge in toddlers and preschool-aged children and include:

  • Developmental Delays: Children may take longer to reach milestones such as walking, talking, or learning new skills. Speech delays are often one of the first noticeable signs.
  • Behavioral Changes: Many children display hyperactivity, restlessness, or difficulty concentrating. This behavior is sometimes mistaken for attention-deficit hyperactivity disorder (ADHD).
  • Recurrent Ear or Sinus Infections: Children may experience frequent infections due to the buildup of GAGs in tissues.

Progressive Symptoms

As the disease advances, symptoms become more severe and difficult for families to manage. These symptoms typically emerge over the following years and may include:

  • Cognitive Decline: Loss of previously learned skills, such as language or problem-solving, becomes evident.
  • Motor Skills Deterioration: Children may lose the ability to walk or perform everyday tasks as the disease affects muscle coordination and strength.
  • Sleep Disturbances: Many children experience difficulty sleeping or disrupted sleep patterns, contributing to behavioral changes.
  • Other Systemic Impacts: These may include coarse facial features, joint stiffness, hearing loss, and gastrointestinal issues.

Diagnosis and Screening

Diagnosing Sanfilippo syndrome involves a combination of clinical evaluations, laboratory tests, and imaging studies performed by healthcare professionals. Discussing options with your healthcare provider ensures access to appropriate and approved diagnostic methods.

  1. Enzyme Assays: Blood or skin samples are analyzed to assess the activity of the enzymes responsible for breaking down GAGs. A deficiency in one of these enzymes confirms the diagnosis and identifies the specific subtype (A, B, C, or D).
  2. Genetic Testing: Genetic tests analyze DNA to identify mutations in the SGSH, NAGLU, HGSNAT, or GNS genes. This confirms the diagnosis and determines the exact subtype. Genetic testing is beneficial for families considering carrier screening or future pregnancies.
  3. MRI Scans: Magnetic resonance imaging (MRI) can detect characteristic changes in the brain caused by GAG accumulation, such as brain atrophy or enlarged ventricles. While not definitive on its own, MRI can support other diagnostic findings.
  4. Urine Tests: Urine tests can reveal elevated levels of GAGs, providing an initial indication of mucopolysaccharidosis. However, this test is not specific to Sanfilippo syndrome and requires follow-up confirmation.

Importance of Early Diagnosis

Early diagnosis is essential for several reasons:

  • Timely Interventions: Early identification allows families to access therapies and supportive care, such as speech or physical therapy, which can help preserve skills for as long as possible.
  • Eligibility for Clinical Trials: Many emerging treatments, such as gene therapies, are most effective when started in the early stages of the disease. A confirmed diagnosis allows children to participate in clinical trials that could slow disease progression.
  • Family Planning: Identifying the genetic cause allows families to make informed decisions around future pregnancies and pursue genetic counseling if needed.

Current Treatments and Research

While there is no cure for Sanfilippo syndrome, treatment approaches focus on symptom management, quality-of-life improvement, and emerging research.

Symptom Management

  • Medications: Anticonvulsants can help control seizures, while behavioral medications may reduce hyperactivity or aggression. Pain management medications can also address joint discomfort.
  • Therapies: Physical therapy helps maintain mobility, while occupational and speech therapies support developmental skills for as long as possible.
  • Surgical Interventions: Some children may require surgeries to address complications such as hearing loss (e.g., ear tubes) or gastrointestinal blockages.

Emerging Gene and Enzyme Replacement Therapies

  • Gene Therapy: Experimental treatments aim to deliver functioning copies of the defective gene directly to cells, allowing them to produce the missing enzyme. Early trials have shown promise in slowing disease progression.
  • Enzyme Replacement Therapy (ERT): This approach involves introducing synthetic versions of the missing enzymes into the body to reduce GAG accumulation. While currently not widely available for Sanfilippo syndrome, ERT is being actively studied in clinical trials.

Experimental therapies mentioned are under investigation in clinical trials and have not yet been approved for widespread use by regulatory agencies such as the FDA.

Care and Support for Families

Caring for a child with Sanfilippo syndrome brings unique challenges, but families don't have to face them alone. 

Accessing support networks, raising awareness, and finding ways to advocate can make a meaningful difference in managing daily life and promoting progress in research and care.

Caregiving Challenges

Families of children with Sanfilippo syndrome often face emotional, physical, and financial challenges in navigating the progression of the disease:

  • Daily Care Needs: Children often require 24/7 care as the disease progresses. Parents and caregivers manage tasks like feeding, bathing, mobility assistance, and administering medications. Sleep disturbances in children can also lead to caregiver exhaustion.
  • Behavioral and Emotional Struggles: Hyperactivity, aggression, and difficulty communicating can make caregiving incredibly demanding. Families often need to adapt their homes to ensure safety.
  • Financial Strain: Families may face a significant financial burden due to medical bills, therapy expenses, and lost income from reduced work hours dedicated to caregiving.

Despite these challenges, many families find strength in community resources, professional support, and advocacy opportunities.

Resources and Support Groups

A range of organizations and networks provide practical assistance and emotional support for families:

Financial resources, such as government assistance programs, nonprofit grants, and crowdfunding platforms, can also help ease the financial strain.

Raising Awareness

Raising awareness about Sanfilippo syndrome and other rare diseases is critical in improving early diagnosis, advancing research, and fostering community understanding.

Families and advocacy groups can organize events, speak at schools or community gatherings, and share personal stories through blogs or social media. These efforts educate the public about the realities of living with a rare disease and the importance of supporting research.

Partnering with healthcare providers to increase awareness among pediatricians and specialists can help improve early detection and referrals to genetic testing.

How You Can Help

Whether you are a family member, friend, or community member, there are many ways to support children and families affected by Sanfilippo syndrome.

Fundraising Ideas

  • Host a charity walk, bake sale, or silent auction to raise money for Sanfilippo research.
  • Set up online fundraisers through platforms like GoFundMe or social media.
  • Work with local businesses to sponsor community events, with proceeds benefiting Sanfilippo foundations.

Volunteer Opportunities

  • Join or start a local support group to connect with families.
  • Provide support with daily tasks, such as running errands or preparing meals for caregivers.
  • Volunteer with organizations like the Cure Sanfilippo Foundation or the National MPS Society.

Communities can impact the lives of families affected by Sanfilippo syndrome by raising awareness, supporting advocacy, and offering hands-on help. Together, we can provide hope and resources while working toward breakthroughs in research and care.

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Key Takeaways

  • Sanfilippo syndrome (Mucopolysaccharidosis Type III) is a rare autosomal recessive genetic disorder.
  • It is characterized by the body's inability to break down glycosaminoglycans (GAGs), leading to progressive damage, especially in the brain and nervous system.
  • Depending on the specific enzyme deficiency, the condition is classified into four subtypes (A, B, C, D). Type A is the most common and severe.
  • Early symptoms often include developmental delays, speech difficulties, and hyperactivity, progressing to cognitive decline, mobility loss, and severe physical impairments in later stages.
  • Diagnosis relies on enzyme assays, genetic testing, and imaging studies, with early detection being critical for accessing supportive therapies, symptom management, and experimental treatments like gene and enzyme replacement therapies currently under research.
  • Families face significant caregiving, emotional, and financial challenges, but support groups, advocacy organizations, and community awareness efforts provide essential resources, connections, and hope for advancements in research and care.
The information in this article is designed for educational purposes only and is not intended to be a substitute for informed medical advice or care. This information should not be used to diagnose or treat any health problems or illnesses without consulting a doctor. Consult with a health care practitioner before relying on any information in this article or on this website.

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