What is Mucopolysaccharidosis-I (MPS I)?

MPS I stands for mucopolysaccharidosis type I. The disease begins in childhood. You can't "catch" it - it depends on your genes.

People with MPS I cannot make a specific protein called alpha-L-iduronidase, which is needed to break down sugars. These sugars accumulate in cells and wreak havoc throughout the body.

People with this condition may have problems growing and functioning of the body, as well as problems with thinking and learning. They may also look different.

Many people with mild MPS can go to school and eventually work and start a family. And even for people with more severe MPS I, there are treatments to help relieve symptoms and slow down the course of the disease.

Because it affects people in different ways, doctors divided MPS I into groups: Hurler syndrome, Hurler-Scheye syndrome, and Scheye syndrome. Now they are talking about a fork between the two forms:

Severe
Attenuated, or less severe

Causes

MPS I is inherited. But you only get it when both parents pass on the broken gene to you.

If you get one normal gene and one "bad" gene, you won't have symptoms of MPS I. However, you can pass the gene on to your children.

Symptoms

Many children with MPS I do not show signs of the disease at first. In people with less severe MPS I, symptoms appear later in childhood. People with this form, attenuated MPS I, can probably make a tiny fraction of the protein, so their symptoms are less severe and the disease progresses very slowly.

Children with a severe form usually begin to show symptoms as early as infancy. They are often large at birth and grow rapidly within a year but then stop at age 3. They will never grow above 4 feet. They also tend to be like:

Shorter than average, with stocky build
Large head, bulging forehead
Thick lips, widely spaced teeth, and large tongue
Short, flat nose with wide nostrils
Thick, tough skin
Short, broad hands with curving fingers
Knock-knees and walking on toes
Curved spine

MPS I can manifest itself in different ways:

Eye problems, including cloudy eyes and a hard time seeing in bright light or at night
Bad breath, dental problems
Weak neck
Breathing problems and airway infections, including runny nose, sinus infections, and sleep apnea
Ear infections and hearing loss
Numbness and tingling in fingers or feet
Heart disease
Stiff joints and trouble moving
Hernias, which look like a bulge around the belly button or in the groin
Diarrhea
Enlarged liver or spleen

Your child may not have all of these symptoms. People with a mild form of the disease usually do not have many physical problems. As a rule, they have normal intelligence and can do many things that other people do.

The more severe the illness, the more likely your child will have these problems. Severe MPS I can also affect intelligence and learning ability. Some children may lose the ability to speak.

Geting a diagnosis

Since this is a rare condition, doctors rule out other conditions first. Your doctor may ask you:

What symptoms have you noticed?
When did you first see them?
Do they come and go?
Does anything make them better? Or worse?
Has anyone in your family had similar symptoms in the past?

If doctors can't find another explanation for your child's symptoms, they will look for MPS I by looking for:

A lot of specific sugar in the urine
How active is the "missing" protein in their blood or skin cells

Once the doctors are convinced that it is MPS I, it is a good idea to let your extended family know about the genetic problem as well.

If you are pregnant and know you are a carrier of the gene, or if you already have a child with MPS I, you can find out if your child is affected. Talk to your doctor about testing in early pregnancy.

Questions for the doctor

Will my child's symptoms change over time? If so, how?
What treatments are best for him now?
Do these treatments have side effects? What can I do about them?
Is there a clinical trial that could help?
How do we check his progress? Are there new symptoms I should watch for?
How often do we need to see you?
Are there other specialists we should see?
If I have more children, how likely are they to have MPS I?

Treatment

Enzyme replacement therapy uses a drug called laronidase (Aldurazyme), an artificial version of the missing protein. This has changed the mindset of many children with MPS I. It can relieve most symptoms and slow the progression of the disease, although it does not help with brain symptoms such as problems with thinking or learning.

Another option may be a hematopoietic stem cell transplant, in which doctors inject new cells into the child's body that can make up for the missing protein. These cells often come from bone marrow or cord blood. When children receive a transplant before the age of 2, they can learn better. But hematopoietic stem cell transplantation cannot solve bone or eye problems.

Work with a doctor who specializes in lysosomal storage disease or lysergic acid diethylamide. Depending on your child's symptoms, you may also need to see other specialists. They often include a cardiologist who specializes in the heart and an ophthalmologist.

Caring for your child

Encourage your child to be independent and make friends. Children with MPS I are often loved and enjoy being with others. Include them in safe family activities.

Most importantly, be positive. Be open-minded about other people's reactions when introducing them to your child. They may not know what to say, perhaps because they don't want to upset, offend, or embarrass you. When people ask about your child, tell them about his condition and what he can and cannot do. Also mention your child's interests, curiosity, and personality.

Talk to your child's school staff to find a personalized learning plan. Your child may need individual attention in class, a special desk, or other accommodations.

To protect the neck, children with MPS should avoid contact sports, gymnastics, trampolining, and similar activities.

Look for ways to change the way your home is set up to make it easier for your child to move around and do things on their own.

Make time for yourself and your family. It's good to have someone to take care of for a while. Take a step back and take a break to rest and recharge.

What to expect

Although there is no cure for MPS I, treatment can improve quality of life, especially if started early. They slow down the disease and help stop the damage before it starts.

Most children with MPS can go to school with other children. They will go through puberty and be able to have children of their own.

When the disease is more severe, it progresses more quickly. Children with the most severe form usually get worse very quickly and may not survive into adolescence. Special care focuses on pain relief and support so that your child and family can have the best quality of life.