Hurler Syndrome (MPS I) in Babies
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published NIH, HRSA, ACMG guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect hurler syndrome (mps i) in babies, here is what the evidence says.
The short answer
Hurler syndrome is the most severe form of mucopolysaccharidosis type I (MPS I), a lysosomal storage disorder caused by deficiency of the enzyme alpha-L-iduronidase. Babies appear normal at birth, but symptoms progressively emerge during the first year of life, including coarse facial features, enlarged liver and spleen, skeletal abnormalities, corneal clouding, heart disease, and intellectual disability. MPS I is on the federal RUSP newborn screening panel. Hematopoietic stem cell transplant performed before age 2 offers the best outcomes, and enzyme replacement therapy with laronidase is also available.
Key takeaways
- Hurler syndrome is the most severe form of mucopolysaccharidosis type I (MPS I), a lysosomal storage disorder caused by deficiency of the enzyme alpha-L-iduronidase. Babies appear normal at birth, but symptoms progressively emerge during the first year of life, including coarse facial features, enlarged liver and spleen, skeletal abnormalities, corneal clouding, heart disease, and intellectual disability. MPS I is on the federal RUSP newborn screening panel. Hematopoietic stem cell transplant performed before age 2 offers the best outcomes, and enzyme replacement therapy with laronidase is also available.
- Usually normal when: Your baby's newborn screening came back normal for MPS I
- Call your doctor if: Your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2
- Varies by age — see the age-by-age breakdown below
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What Parents Should Know
According to NIH, HRSA, ACMG guidelines, hurler syndrome is the most severe form of mucopolysaccharidosis type I (MPS I), a lysosomal storage disorder caused by deficiency of the enzyme alpha-L-iduronidase. Babies appear normal at birth, but symptoms progressively emerge during the first year of life, including coarse facial features, enlarged liver and spleen, skeletal abnormalities, corneal clouding, heart disease, and intellectual disability. MPS I is on the federal RUSP newborn screening panel. Hematopoietic stem cell transplant performed before age 2 offers the best outcomes, and enzyme replacement therapy with laronidase is also available. At 0-3 months, babies with Hurler syndrome typically appear normal at birth. Some may have umbilical or inguinal hernias, which are common in MPS I but also common in the general population, so they may not raise immediate concern. Newborn screening can detect MPS I through enzyme activity measurement. If your baby's newborn screen is positive for MPS I, confirmatory testing including enzyme assay and genetic testing will determine the specific form (Hurler, Hurler-Scheie, or Scheie). Early diagnosis is critical because stem cell transplant outcomes are best when performed before significant symptoms develop. It is generally considered normal when your baby's newborn screening came back normal for MPS I. However, you should contact your pediatrician promptly if your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2.
Normal vs. Concerning
When to Seek Immediate Care
- Your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2
- Your baby has coarse facial features, an enlarged liver and spleen, corneal clouding, and appears to be falling behind developmentally — seek evaluation by a geneticist or metabolic specialist
- Your child with known Hurler syndrome develops signs of spinal cord compression (difficulty walking, loss of bladder control, weakness in arms or legs) — this requires emergency evaluation
By Age
What to expect by age
0-3 months
Babies with Hurler syndrome typically appear normal at birth. Some may have umbilical or inguinal hernias, which are common in MPS I but also common in the general population, so they may not raise immediate concern. Newborn screening can detect MPS I through enzyme activity measurement. If your baby's newborn screen is positive for MPS I, confirmatory testing including enzyme assay and genetic testing will determine the specific form (Hurler, Hurler-Scheie, or Scheie). Early diagnosis is critical because stem cell transplant outcomes are best when performed before significant symptoms develop.
3-6 months
Early subtle signs may begin to emerge. Babies may have frequent upper respiratory infections, chronic runny nose, and recurrent ear infections due to glycosaminoglycan (GAG) storage in tissues. Some parents notice that their baby's facial features seem to be getting coarser over time — a broader nose, thickened lips, and a larger head. Hepatosplenomegaly (enlarged liver and spleen) may be detected on exam. If MPS I is suspected, urine GAG testing and enzyme assays can confirm the diagnosis.
6-12 months
The progressive nature of Hurler syndrome becomes more apparent. Facial features become noticeably coarse. Joint stiffness, particularly in the hands (claw-hand deformity), begins to develop. Corneal clouding may become visible, affecting vision. Developmental progress may slow. Skeletal changes visible on X-ray (dysostosis multiplex) are often present. This is a critical window for hematopoietic stem cell transplant (HSCT), which is most effective when performed before age 2 and ideally before significant cognitive decline.
1-2 years
Without treatment, children with Hurler syndrome show progressive intellectual disability, worsening joint stiffness, characteristic skeletal changes, cardiac valve disease, and increasing hepatosplenomegaly. Hearing loss is common. If HSCT has not yet been performed, this remains a viable window, though outcomes are best when transplant occurs earlier. Enzyme replacement therapy (laronidase) is often started before transplant and can help reduce GAG storage. After successful HSCT, many children show stabilization or improvement in cognitive function.
2 years and beyond
Children who received early HSCT often maintain cognitive development and have slower progression of skeletal and cardiac disease, though they may still need orthopedic interventions, cardiac monitoring, and therapies. Without transplant, Hurler syndrome typically leads to severe disability, with most children not surviving past the first decade. The milder forms of MPS I (Hurler-Scheie and Scheie syndromes) have a slower course, with normal or near-normal intelligence, and are managed with enzyme replacement therapy and supportive care.
What to Tell Your Pediatrician
- Describe when you first noticed hurler syndrome (mps i) in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby received an abnormal MPS I result on newborn screening — follow up promptly as early intervention dramatically improves outcomes.
- Mention if your baby has recurrent ear infections, persistent runny nose, and you notice their facial features seem to be changing or becoming coarser.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby's newborn screening came back normal for MPS I
- An initial positive screen was followed by confirmatory testing that showed normal enzyme levels
- Your baby has an umbilical hernia but no other signs of MPS I — hernias are very common in otherwise healthy babies
- Your child had successful HSCT for Hurler syndrome and is developing well with stable enzyme levels
- Your baby received an abnormal MPS I result on newborn screening — follow up promptly as early intervention dramatically improves outcomes
- Your baby has recurrent ear infections, persistent runny nose, and you notice their facial features seem to be changing or becoming coarser
- Your baby has progressive joint stiffness, especially in the hands, along with an enlarged abdomen
- There is a family history of MPS I or another mucopolysaccharidosis
- Your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2
- Your baby has coarse facial features, an enlarged liver and spleen, corneal clouding, and appears to be falling behind developmentally — seek evaluation by a geneticist or metabolic specialist
- Your child with known Hurler syndrome develops signs of spinal cord compression (difficulty walking, loss of bladder control, weakness in arms or legs) — this requires emergency evaluation
What You Can Do at Home
- Keep track of when you notice hurler syndrome (mps i) in babies — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby's newborn screening came back normal for MPS I — this is generally within the range of normal.
- At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2.
Related Conditions
Abnormal Newborn Screening Results
An abnormal or positive newborn screening result means that further testing is needed, not that your baby definitely has a condition. Most positive screens turn out to be false positives after confirmatory testing. Newborn screening tests are intentionally sensitive to avoid missing any affected babies, so follow-up testing is essential to determine whether the result is a true positive.
Signs of a Metabolic Disorder in Babies
Metabolic disorders (inborn errors of metabolism) occur when the body cannot properly process certain nutrients or chemicals. Many are detected through newborn screening. Signs can include poor feeding, vomiting, lethargy, seizures, unusual body or urine odor, failure to thrive, developmental regression, and metabolic crises triggered by illness or fasting. Early detection and treatment are crucial, as many metabolic disorders are manageable with dietary modifications and medical treatment.
Related Resources
Frequently asked questions
Is hurler syndrome (mps i) in babies normal?
When should I call the doctor about hurler syndrome (mps i) in babies?
When is hurler syndrome (mps i) in babies normal?
What causes hurler syndrome (mps i) in babies?
What should I mention to my pediatrician about hurler syndrome (mps i) in babies?
Is hurler syndrome (mps i) in babies normal at 0-3 months?
Is hurler syndrome (mps i) in babies normal at 3-6 months?
Should I go to the ER for hurler syndrome (mps i) in babies?
Does hurler syndrome (mps i) in babies go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Hurler Syndrome (MPS I) in Babies.
Things to mention
- Describe when you first noticed hurler syndrome (mps i) in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby received an abnormal MPS I result on newborn screening — follow up promptly as early intervention dramatically improves outcomes.
- Mention if your baby has recurrent ear infections, persistent runny nose, and you notice their facial features seem to be changing or becoming coarser.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Your baby received an abnormal MPS I result on newborn screening — follow up promptly as early intervention dramatically improves outcomes
- Your baby has recurrent ear infections, persistent runny nose, and you notice their facial features seem to be changing or becoming coarser
- Your baby has progressive joint stiffness, especially in the hands, along with an enlarged abdomen
Urgent signs to report immediately
- Your newborn has screened positive for MPS I — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2
- Your baby has coarse facial features, an enlarged liver and spleen, corneal clouding, and appears to be falling behind developmentally — seek evaluation by a geneticist or metabolic specialist
- Your child with known Hurler syndrome develops signs of spinal cord compression (difficulty walking, loss of bladder control, weakness in arms or legs) — this requires emergency evaluation
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
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Related Resources
Bottom line
Most cases of hurler syndrome (mps i) in babies are normal. Talk to your pediatrician if your newborn has screened positive for mps i — confirmatory testing should happen urgently because transplant outcomes depend on early treatment, ideally before age 2.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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Related Medical Concerns
Abnormal Newborn Screening Results
An abnormal or positive newborn screening result means that further testing is needed, not that your baby definitely has a condition. Most positive screens turn out to be false positives after confirmatory testing. Newborn screening tests are intentionally sensitive to avoid missing any affected babies, so follow-up testing is essential to determine whether the result is a true positive.
Signs of a Metabolic Disorder in Babies
Metabolic disorders (inborn errors of metabolism) occur when the body cannot properly process certain nutrients or chemicals. Many are detected through newborn screening. Signs can include poor feeding, vomiting, lethargy, seizures, unusual body or urine odor, failure to thrive, developmental regression, and metabolic crises triggered by illness or fasting. Early detection and treatment are crucial, as many metabolic disorders are manageable with dietary modifications and medical treatment.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.
Adenoid Hypertrophy and Breathing
Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.
Adrenoleukodystrophy (ALD) in Babies
X-linked adrenoleukodystrophy (X-ALD) is a genetic disorder affecting about 1 in 17,000 newborns, caused by mutations in the ABCD1 gene on the X chromosome. It primarily affects boys and impairs the breakdown of very long-chain fatty acids (VLCFAs), which accumulate and damage the myelin sheath in the brain and the adrenal glands. The most severe form, cerebral ALD, typically affects boys between ages 4-10 with rapid neurological decline. Newborn screening now enables early detection, and hematopoietic stem cell transplant or gene therapy performed before significant brain involvement can be life-saving.