The Systemic Effects of Hunter Syndrome

Hunter Syndrome can have a wide range of effects on the body, and not many of them are good.
This might seem ironic since the cause of Hunter Syndrome is pretty much just a missing enzyme in a lysosome, but once you consider how this enzyme is used all over the body, the wide ranging effects of Hunter Syndrome start to make sense.

Some of the more prominent physical changes in a Hunter Syndrome patient

Hunter Syndrome will also result in several physical changes as a patient grows, which are easily identifiable and characteristic of the disease.

• A prominent forehead and nasal bridge
• Thickened tongue
• Shorter stature due to bone deformities
• Broad chest
• Abdominal hernias, where some organs protrude out of the body cavity

Hunter Syndrome is know to affect large swathes of the body, some of the most commonly affected systems are

• The Nervous System
• The Skeletal System
• The Respiratory System

Effects on the Nervous System

The accumulation of Glycosaminoglycan(GAG) molecules in the brain interferes with the complex, delicate biochemical pathways involved in brain development. As the early years of a child are one of the most important periods of brain development, this usually results in stunted mental development, profound mental retardation as well as loss of certain cognitive functions.

Accumulation of GAG molecules can lead to irreversible mental retardation if left untreated

In addition, there may be a buildup of excess fluids in the brain, pressure from these fluids are known to affect the eyes as well as certain sections of the brain. This can cause severe headaches, interfere with vision and lead to various behavioral changes

The membranes that surround the spinal cord may become thick and scarred due to an excessive buildup of GAG around it. This causes pressure and compression of the upper spinal cord leading to fatigue in the legs and gradual weakening.

Effects on the Skeletal system

By far the most commonly affected system, all Hunter Syndrome patients experience some degree of skeletal problems, with the most commonly affected being

• The major joints such as the shoulder, elbow, wrist, hips and knees
• The skeletal structure

Accumulation of GAG molecules on the joints reduces the range of motion that joint is capable of, causing stiffness, reduced flexibility and possibly compressing the nerves around that area

This can lead to other secondary symptoms such as carpal tunnel syndrome.

The bone structure may also be deformed by excessive accumulation of GAG molecules, which generally results in stunted growth, broadening of the ribcage and of the skull.

Effects on the Respiratory and Circulatory System

One reason Hunter Syndrome can be extremely debilitating is due to tissue swelling caused by accumulation of GAG molecules. This is especially serious where the respiratory and circulatory system are concerned, as these systems are responsible for the distribution of oxygen around the body.

Common symptoms of respiratory stress include an enlarged tongue and thickening of the nasal passages and windpipe, which all serve to make breathing difficult by obstructing the flow of air into the lungs.. Respiratory infections and pneumonia are common side effects of this as well. Sleep apnea, a condition in which breathing is intermittently interrupted during sleep, is also often a common occurrence due to airway constriction.

Another effect of tissue thickening associated with Hunter Syndrome is the gradual thickening of the blood vessels in the heart.

In particular, the aorta and other associated blood vessels progressively get narrower, which leads to serious side effects such as heightened blood pressure levels.

If the heart valves are affected by this thickening, they may no longer be able to function normally due to the now irregular shape preventing proper closure of these valves. As a result, the heart is unable to efficiently pump blood to other parts of the body. This condition will gradually worsen and eventually lead to heart failure.

Heart valves are particularly susceptible to GAG buildup,
this can interfere with how the heart pumps blood to the rest of the body

So as you can see, Hunter Syndrome is an extremely debilitating disease which causes a whole lot of problems if left unchecked. Fortunately, with early diagnosis, many of these symptoms can be relieved to some extent.

But how exactly do we diagnose this disease?

Next up: Diagnosing Hunter Syndrome

Sources:
http://www.sleepapnoea.respironics.eu/media/what_is_osa.gif
http://images.medicinenet.com/images/ccf/42350_heartvalves.jpg

http://www.mayoclinic.org/diseases-conditions/hunter-syndrome/basics/complications/con-20026538

http://rarediseases.about.com/cs/huntersyndrome/a/022204.htm