MPS IV (Morquio syndrome)
MPS IV is one of the mucopolysaccharide diseases and is also known as Morquio syndrome. MPS IV takes its name from Dr. Morquio, a pediatrician in Montevideo, Uruguay, who in 1929 described a family of four children affected by this condition. As the same condition was also described in the same year by Dr. Brailsford from Birmingham, England, it is sometimes known as Morquio-Brailsford syndrome.
There is no cure for MPS diseases, but there are ways of managing and treating the problems they cause.
What causes this disease?
Mucopolysaccharides are long chains of sugar molecule used in the building of connective tissues in the body.
“saccharide” is a general term for a sugar molecule (think of saccharin)
“poly” means many
“muco” refers to the thick jelly-like consistency of the molecules
There is a continuous process in the body of replacing used materials and breaking them down for disposal. Children with MPS IV are missing an enzyme which is essential in cutting up the mucopolysaccharides called keratan sulfate. The incompletely broken down mucopolysaccharides remain stored in cells in the body causing progressive damage. Babies may show little sign of the disease, but as more and more cells become damaged, symptoms start to appear.
How common is MPS IV?
MPS IV is one of the rarest of the MPS diseases in the United States. Reliable incidence figures are not available, but estimates have varied between 1 in 200,000 live births to 1 in 300,000 live births.
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. MPS IV is caused by a recessive gene. If an adult carrying the abnormal gene marries 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 be affected with the disease. There is a two in three chance that unaffected brothers and sisters of children with MPS IV will be carriers. They can be reassured, however, that as the disease is so rare, the chance of marrying another carrier is very slight provided they do not marry a cousin or other close family member.
Is there a treatment for MPS IV?
In 2014 Vimizin was approved by the FDA as a enzyme replacement therapy for MPS IVA. Currently we do not have a treatment for MPS IVB.
Is there a cure for MPS IV?
There is no cure.
All families of affected children should seek further information from their doctor or a Genetic Counselor.