Hurler Disease (“Mucopolysaccharidosis type 1H” or “MPS1H”)

In Ontario, every baby has a few drops of blood taken from their heel when they are about a day old.  The blood is tested for more than 25 treatable diseases, including one called “mucopolysaccharidosis type 1H” or “MPS1H”.

Screening for MPS1H started in late July 2020.

A screen positive result means that the baby may have MPS1H and more tests are needed to be sure. Screening is important because babies with MPS1H can be healthier if they are identified and treated early.

• MPS1H is often called Hurler disease.  It is part of a group of rare genetic diseases called “lysosomal storage diseases”
• Babies with MPS1H are not able to make an enzyme called alpha-L-iduronidase (IDUA)
• IDUA helps to break down long chains of sugars called glycosaminoglycans (GAGs) into smaller pieces.
• When the IDUA enzyme is not working, GAGs build-up and cause problems in the heart, brain, bones, eyes, ears and other parts of the body
• There are also less severe or “attenuated” forms, often called Hurler-Scheie (MPS1HS) or Scheie (MPS1S) Disease.  Babies with these less severe forms usually do not need treatment at an early age.
• MPS1H, MPS1HS, and MPS1S are all forms of MPS1 and happen when a person’s body cannot make IDUA.

• A screen positive result means that the baby may have a form of MPS1 and more testing is needed to be sure.   
• It is natural for parents and guardians to feel worried and have questions when their baby has a screen positive result.
• The baby’s health care provider or a health care provider at a newborn screening regional treatment centre will discuss the screening results with the baby’s family.
• Follow-up testing is arranged as soon as possible and usually involves blood and urine tests, and an assessment with a metabolic doctor.
• It can take a few days to weeks to find out if a baby truly has MPS1H or not.  It can also take more time to figure out if a baby has MPS1H or one of the less severe forms of the disease. This waiting period can be hard for families. 

• Abnormal – the baby has a form of MPS1 and should get care from a metabolic doctor.  A metabolic doctor, along with other specialists, will discuss what follow-up is best for the baby.
• Normal – in some cases, the follow-up test results show that the baby does not have a form of MPS1.
• Inconclusive - more testing is needed to figure out if the baby has a form of MPS1.  The family will be supported by a metabolic specialist who will make sure that appropriate follow-up takes place.

Babies with MPS1H usually have no signs or symptoms at birth.  

Symptoms of MPS1H usually develop in the first year of life and tend to get worse quickly.   Individuals with MPS1HS or MPS1S usually start to show symptoms later in childhood.  Symptoms of MPS1HS or MPS1S are milder and do not involve the brain.

Common symptoms of MPS1H include:

• Developmental delay
• Thickening of the bones, and stiffness of the joints all over the body
• Large head, clouding of the eyes, and distinctive facial features
• Frequent ear infections and hearing loss
• Enlarged liver and spleen
• Hernia (soft out-pouching around the belly button or lower abdomen)
• Thickening of the muscles of the heart and heart valve problems

The main goal of screening is to help find children who have MPS1H earlier.  Children with MPS1H can benefit from being identified early and getting treatment sooner.

Children with MPS1H are followed closely by a team of doctors and health care providers because many different parts of the body can be affected, and symptoms can show up over time.

When treatment for MPS1H is started early, some symptoms can be prevented, and others can be improved or stabilize.  Some symptoms can get worse over time and treatment can help to slow this down.

Treatment for MPS1H involves getting IDUA enzyme that works into the body. There are two main ways to get working IDUA enzyme into the body:

• bone marrow transplant (also called hematopoietic stem cell transplant)
• Enzyme replacement therapy

Therapies to help treat the symptoms of MPS1H are also important and can include:

• Physical therapy and exercise to help with joint movement
• Surgery to remove the tonsils and adenoids to help with breathing problems
• Surgery to insert ear tubes to help prevent infections
• Hearing aids for those with hearing loss

• Treatment may allow babies to lead healthier lives and help to reduce or prevent symptoms of MPS1H
• Even with treatment, children with MPS1H can develop new health issues and some of their symptoms can get worse.