Sanfilippo

Society for Mucopolysaccharide Diseases
MPS House, Repton Place, White Lion Road, Amersham, Buckinghamshire, HP7 9LP, UK
Tel: 0845 389 9901 Fax: 0845 389 9902
National Registered Charity No. 287034

Sanfilippo Disease (MPS III)

Sanfilippo disease is a mucopolysaccharide disease also known as MPS lll. It takes its name from Dr. Sanfilippo who was one of the doctors from the United States who described the condition in 1963.

What causes this disease?
There is a continuous process in the body of replacing used materials and breaking them down for disposal. Children with Sanfilippo disease are missing an enzyme which is essential in cutting up the used mucopolysaccharides. The incompletely broken down mucopolysaccharides remain stored in cells in the body causing progressive damage. Babies and small children may show little sign of the disease but, as more and more cells become damaged, symptoms start to appear.

Are there different forms of the disease?
To date four different enzyme deficiencies have been found to cause Sanfilippo disease and so the condition is described as type A,B,C or D. Type A is the most common form found in most populations.

MPS lllA is missing the enzyme heparan N sulphatase
MPS lllB is missing alpha-N-acetylglucosaminidase
MPS lllC is missing acetyl-CoA: alpha-glucosaminide acetyltransferase
MPS lllD is missing N-acetylglucosamine-6-sulphatase

However it is important to note that there are no significant clinical (physical) differences between the different subtypes of MPS III, although there have been some very mild cases of the B form where the sufferers have remained relatively unaffected into adult life. The latest understanding is that some people seem to produce some enzyme activity which helps to slow down the progression of the disease while those with more severe symptoms appear to have no enzyme activity at all.

How common is Sanfilippo disease?
The MPS Society which co-ordinates the Registry for Mucopolysaccharide and Related Diseases has shown that this is a rare condition affecting one in 85,000 live births. Over a ten-year period between 1980 and 1990, 88 babies with Sanfilippo disease were born in the United Kingdom.

How is the disease inherited?
We all have genes inherited from our parents which control whether we are tall, short, fair etc. Some genes we inherit are 'recessive', that is to say we carry the gene but it does not have any effect on our development. Sanfilippo disease is caused by a recessive gene. If an adult carrying the abnormal gene has a partner who is another carrier there will be a one in four chance with every pregnancy that the child will inherit the defective gene from each parent and will suffer from the disease. There is a two in three chance that unaffected brothers and sisters of Sanfilippo sufferers will be carriers. They can be reassured however that, as the disease is so rare, the chance of having a partner who is another carrier is very slight provided this partner is not a cousin or other blood relative.

All families of affected children should seek further information from their doctor or from a genetic counsellor before planning to have more children. There is a more detailed explanation of this complex subject in a booklet on the Pattern of Inheritance available from the MPS Society.

Prenatal diagnosis
If you already have a child with Sanfilippo disease it is possible to have tests during a subsequent pregnancy to find out whether the baby you are carrying is affected. It is important to contact your doctor as soon as you suspect you may be pregnant if you wish tests to be arranged. If you have any difficulties please contact the Society without delay.

Is there a cure?
At present there is no cure for any of the mucopolysaccharide diseases. Various experimental methods have been used to try to replace the missing enzyme, but none has so far been of any significant long-term benefit. Bone marrow transplant has been tried on Sanfilippo patients, but with disappointing results and is now never recommended for this condition.

How does the disease progress?
The disease will affect children differently and its progress will be much faster in some cases than in others. Change will usually be very gradual and therefore easier to adjust to. However some changes could occur quickly and be followed by a period of time before further changes occur. This is referred to as a plateau stage. The disease tends to progress through three main stages.

The first during the child's pre-school years may be a very frustrating one for the parents. They begin to worry as their child starts to lag behind their friends' children in development and they may feel they are being blamed for the child's overactive and difficult behaviour.

The diagnosis is often made very late as some children do not look in any way different and their symptoms such as diarrhoea, frequent respiratory and ear infections and boisterous behaviour are among the most common seen in all children. The doctor has to be perceptive enough to recognise that something serious is wrong and to ask for urine and blood tests to help reach a diagnosis. It is not unusual for families to have had more than one affected child before the diagnosis is established.

The second phase of the disease is characterised by extremely active, restless and often very difficult behaviour. Some children sleep very little at night. Many will be into everything and one parent writes 'taps are a great favourite, we're always having floods'. Many like to chew; hands clothes or anything they can get hold of 'even the contents of ashtrays are not missed out.'

Sadly, language and understanding will gradually be lost and parents may find it hard not being able to have a conversation with their child. Many will find other ways of communicating, perhaps using sign language such as the Makaton system. 'She loves me to talk to her and she smiles with her eyes, almost talks with them and her whole face lights up with love.' Some children never become toilet trained and those who do will eventually lose this ability.

In the third phase of the disease Sanfilippo children begin to slow down. They become more unsteady on their feet, tending to fall frequently as they walk or run. Eventually they lose the ability to walk. Life may be more peaceful in some ways, but parents will need help with the physically tiring task of caring for an immobile child or teenager and with all the changes necessary to provide for their care.

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