Hunter disease is one of the mucopolysaccharide diseases and is
also known as MPS Type II. Hunter disease takes its name from Charles
Hunter, the professor of Medicine in Manitoba, Canada, who first
described two brothers with the disorder in 1917.
What causes this disease?
Mucopolysaccharides are long chains of sugar molecules 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
and '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 II are missing
an enzyme called iduronate sulphate sulphatase which is essential
in cutting up the mucopolysaccharides called dermatan and heparan
sulphate. 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 is this disease inherited ?
Hunter disease has a different form of inheritance from all the
other MPS diseases as it is 'sex linked' like haemophilia. Girls
may be carriers of the disease but, except in very rare cases, only
boys will be sufferers. The few girls who have been found to have
the disease have an associated chromosomal abnormality.
All families of children with Hunter disease should seek further
information from their doctor or from a genetic counsellor before
planning to have more children. If the mother is a carrier there
is a 1 in 2 risk that any boy born to her will have the disease and
that any girl will be a carrier.
The sisters and maternal aunts of an individual with MPS II may
be carriers of the disease who would also have a 1 in 2 chance of
passing the disease to a son.
In many families it is possible to detect female carriers by direct
analysis of the genetic material. The doctor may wish to take a sample
of blood from your affected child so that the exact genetic abnormality
can be detected.