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Recognizing MPS VI

No single symptom defines MPS VI. Instead, the person with MPS VI may develop a cluster of several symptoms affecting various body systems. The symptoms of MPS are not usually evident at birth but show up later as GAG builds up. The rate at which symptoms appear and worsen varies widely. Some affected individuals have a rapidly advancing form of MPS VI, and may start showing symptoms as early as 6 to 24 months of age. Others have a more slowly advancing form of MPS VI, and may not show significant symptoms until much later.1,2

Could I have MPS VI?

Diagnosis of MPS disorders tends to be delayed. In a survey of MPS I families, an average delay of 2.5 years from the time when symptoms first appeared to the time when MPS was suspected was reported. Several factors contribute to this delay in diagnosis. First of all, the early signs of MPS VI can be subtle—the early signs of slowly advancing MPS VI, in particular, are difficult to recognize. Another important factor is the variability of symptoms, meaning that not all MPS VI individuals have exactly the same symptoms. In addition, some of the early symptoms, such as frequent ear infections, are commonly seen in children who do not have MPS. A very important reason for delay in diagnosis may be the rarity of this disease—doctors rarely or never see a person with MPS and so are less likely to suspect it.1,3

MPS VI typically produces several telltale signs and symptoms that should prompt a specialist to suspect MPS VI—and order laboratory tests that will confirm the diagnosis. Those signs and symptoms may include pronounced facial features, frequent ear infections, and skeletal changes. These and other features are described below.

It's important to remember that not all MPS VI individuals have all of the problems listed below. While some MPS VI individuals look very similar and have similar medical problems, there can also be wide variation in the number and severity of symptoms that MPS VI individuals experience.

Signs and Symptoms

Appearance

MPS VI often produces a range of recognizable changes in physical appearance. You may have heard the term "coarse facial features"—this refers to the thickening of the nose, lips, and tongue that occurs as GAG builds up in tissue. MPS VI individuals may have a large head, a protruding abdomen, and are usually short.

Growth

Every person with MPS VI is different. Babies with MPS VI usually begin growing at an average rate, but as early as the first 2 to 3 years of life their growth may slow down dramatically, and may stop completely by the age of 6 or 8 years. People with rapidly advancing MPS VI may reach a final height of 3 to 4 feet (90 to 140 centimeters), while people with more slowly advancing disease often grow taller.1

Brain and Nerves

MPS VI does not affect intelligence. However, hearing difficulties, vision problems, and fatigue can interfere with learning in a classroom setting.1

MPS VI-affected people may, over time, develop hydrocephalus, a brain complication that can be quite serious. In hydrocephalus, the amount of fluid in the brain builds up causing pressure on the brain. Hydrocephalus can show up in various ways, including drowsiness, headache, and behavioral changes, and can cause permanent damage if not corrected.4

Compression of the spinal cord is another serious complication of MPS VI. This can occur due to storage of GAG in the tissue around the spinal cord and as a result of the bony changes along the spine. Pressure or pinching of the spinal cord can cause weakness or paralysis if left untreated.

Carpal tunnel syndrome (CTS) occurs when GAG storage and changes in the bones of the wrist cause pressure on the nerve that passes through the wrist. Numbness, pain, and loss of hand function usually accompany untreated CTS; symptoms in people affected by MPS may be different from symptoms that are typically seen in people without MPS.

Eyes and Ears

Individuals with MPS VI frequently develop clouding in the front part of their eyes, called their corneas, and this can cause their vision to decline. Vision problems can also be caused by glaucoma or damage to the optic nerve or the retina. Hearing loss is also common, due to frequent ear infections and changes in the structure of the middle ear.1,4

Teeth

Children with MPS VI can experience dental problems. Their teeth tend to be small and spaced widely apart, with poorly formed enamel. New teeth that are coming in often fail to push their way out of the gums. This can cause frequent infections in the mouth.5

Breathing and Respiratory System

People with MPS VI often have difficulty breathing or exhibit noisy breathing and snoring. This occurs because their trachea—the airway that connects their lungs with their mouth—becomes narrow over time. Enlarged tonsils and adenoids may also obstruct the flow of air. As a result, they may develop a condition called sleep apnea, where their breathing stops and restarts many times each night, causing periods of low oxygen levels and poor sleep.1

Chest and sinus infections are also frequent. Poor airflow due to airway obstruction and chest constriction from stiff ribs, along with excess mucus secretions, all contribute to frequent respiratory infections.1,6,7

Heart

Over time, storage of GAG may cause people with MPS VI to develop heart problems, including malfunctioning heart valves (particularly the mitral and aortic valves), thickening and stiffening of the heart wall, and narrowing of the blood vessels that pick up oxygen in the lungs and supply the heart muscle with blood. These problems can lead to heart failure—a condition in which the heart can no longer pump strongly enough to deliver blood—and oxygen—to the rest of the body.1

Abdomen

The livers and spleens of people with MPS VI become enlarged over time—a result of storage of GAG in these organs. This enlargement of the liver is called hepatomegaly, and enlargement of the spleen is called splenomegaly. Although enlargement of the liver and spleen do not normally affect the function of either organ, their enlargement can cause a person's abdomen to bulge. The liver can become large enough to put pressure on the stomach, causing a feeling of fullness, or on the lungs, reducing the individual's ability to move air in and out well.1,8

MPS VI also causes weakness in the abdominal muscles, and so babies and children with the disorder develop inguinal hernias (hernias in the groin) and umbilical hernias (hernias in the navel).

Bones and Joints

The accumulation of excess GAG causes problems with the bones and joints. Joints become stiff, especially the knees, hips, and elbows, causing people with MPS VI to take on a flexed-knee, hunched posture when they stand. Progressive joint stiffness may cause pain and limit movement. Fingers may bend and stiffen, resulting in poor hand and finger dexterity.1

MPS VI also produces skeletal (bone) changes that can be seen by X-ray and are collectively called dysostosis multiplex. These changes affect the ribs and vertebrae (bones that make up the spine). Affected vertebrae can lead to curvature of the spine or slippage of the vertebrae with pinching of the spinal cord. Stiff and unusually shaped ribs make it difficult to move air in and out of the lungs well, and contribute to the tendency of MPS VI individuals to experience frequent respiratory infections.

Exercise Tolerance

People with MPS VI may tend to tire easily and have low tolerance for physical activity. This happens for a variety of reasons, including problems with joint pain and stiffness, breathing problems, and heart problems.1

Disease Progression

Level of disability and life expectancy vary greatly in individuals with MPS VI. In some MPS VI individuals, the disease involves many different medical problems, and progresses rapidly. In others, the disease is less severe and progresses at a slower rate. Regular evaluations and prompt medical treatment, provided by a team of specialists that includes an MPS expert, will help to avoid serious complications and improve quality of life.1

  1. Neufeld EF, Muenzer J. The mucopolysaccharidoses. In: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The Metabolic and Molecular Bases of Inherited Disease. Vol 3. 8th ed. New York, NY: McGraw- Hill; 2001:3421-3452.
  2. Paterson DE, Harper G, Weston HJ, Mattingley J. Maroteaux-Lamy syndrome, mild form—MPS vi b. Br J Radiol. 1982;55:805-812.
  3. MPS I survey results: patterns in the referral, diagnosis, and management of individuals with MPS I. National MPS Society and Genzyme Corporation. April 2004. Available at: http://www.mpssociety.org/content/4010/Library/.
  4. Vougioukas VI, Berlis A, Kopp MV, et al. Neurosurgical interventions in children with Maroteaux-Lamy syndrome. Case report and review of the literature. Pediatr Neurosurg. 2001;35:35-38. Review.
  5. Smith KS, Hallett KB, Hall RK, et al. Mucopolysaccharidosis: MPS VI and associated delayed tooth eruption. Int J Oral Maxillofac Surg. 1995;24:176-180.
  6. Miller G, Partridge A. Mucopolysaccharidosis type VI presenting in infancy with endocardial fibroelastosis and heart failure. Pediatr Cardiol. 1983;4:61-62.
  7. Fletcher J, Pamula Y, Martin AJ. Reversing respiratory disease in MPS: lessons from bone marrow transplantation. Poster accessed at www.chempathadelaide.com.au.
  8. Sjogren P, Pedersen T, Steinmetz H. Mucopolysaccharidoses and anaesthetic risks. Acta Anaesthesiol Scand. 1987;31:214-218. Review.
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