Everything You Need To Know About MPS2

What is MPS2? (Hunter Syndrome)

Hunter syndrome is a rare genetic disorder that occurs when an enzyme your body needs is either missing or doesn’t work properly.

1622818_10203236952391167_814988113_nBecause the body doesn’t have enough of the enzyme to break down certain complex molecules, the molecules build up in harmful amounts in certain cells and tissues. The buildup that occurs in Hunter syndrome eventually causes permanent, progressive damage affecting appearance, mental development, organ function and physical abilities.

Hunter syndrome appears in children as young as 18 months. It nearly always occurs in males.

There is no cure for Hunter Syndrome or any of the MPS diseases. Treatment of Hunter syndrome involves management of symptoms and complications.

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What Are Some Symptoms of MPS2?

Hunter syndrome is one type of a group of inherited metabolic disorders called mucopolysaccharidosis (MPS), and Hunter syndrome is referred to as MPS II. Hunter syndrome symptoms vary from person to person. Some people have mild symptoms, while others have severe problems. Symptoms aren’t present at birth. If symptoms begin early — around ages 2 to 4 — the syndrome is usually more severe.

Signs and symptoms may include:

  • Delayed development, such as late walking or talking
  • Changing facial features, including thickening of the lips, tongue and nostrils
  • A broad nose and flared nostrils
  • Claw-like hands
  • A protruding tongue
  • Abnormal bone size or shape and other skeletal irregularities
  • Enlarged internal organs, such as the liver and spleen, resulting in a distended abdomen
  • Respiratory difficulties including sleep apnea, a condition in which breathing intermittently stops during sleep
  • Cardiovascular disorders, such as progressive thickening of heart valves, high blood pressure (hypertension) and obstruction of blood vessels
  • Vision damage or loss from degeneration of cells that capture light and buildup of cellular debris in the brain causing pressure on the optic nerve and eye
  • Progressive loss of hearing
  • Aggressive behavior
  • Stunted growth
  • Joint stiffness
  • Diarrhea
  • Carpal tunnel syndrome
  • Sleep apnea
What Causes MPS2?

Hunter syndrome develops when a defective chromosome is inherited from the child’s mother. Because of that defective chromosome, an enzyme that’s needed to break down complex sugars called glycosaminoglycans is missing or malfunctioning.

The missing or malfunctioning enzyme is called iduronate-2-sulfatase.

In unaffected people, these enzymes are found in parts of the body’s cells known as lysosomes. The lysosomes use enzymes to break down glycosaminoglycans, as part of the body’s normal recycling and renewal process. In a person with Hunter syndrome or another form of MPS, these enzymes either are missing or don’t work correctly.

Normally, the nutrients that are broken down by lysosomes help your body build bone, cartilage, tendons, corneas, skin and connective tissue, and the fluid that lubricates your joints.

When this enzyme isn’t working properly, undigested glycosaminoglycans collect in the cells, blood and connective tissues, causing permanent and progressive damage. Hunter syndrome and other forms of MPS are sometimes called lysosomal storage diseases.

Signs and Symptoms of MPS2

The age of onset and severity of Mucopolysaccharidosis type II (MPS II) differ depending on the form. Signs of severe MPS II usually begin between ages two and four.

The symptoms of Hunter syndrome (MPS II) are generally not apparent at birth, but usually start to become noticeable after the first year of life.

Since these symptoms are quite common among all infants, they are not likely to lead a doctor to make a diagnosis of Hunter syndrome right away. As the buildup of GAG continues throughout the cells of the body, signs of Hunter syndrome become more visible.

Common childhood occurrences BUT early symptoms of Hunter syndrome:

  • inguinal hernia
  • ear infections
  • runny nose
  • difficulty breathing
  • heart murmur

MPS II has a wide range of symptoms that vary in severity.

Physical appearances of many children with Hunter syndrome include a distinctive coarseness in their facial features (full lips & large rounded cheeks), including a prominent forehead, a nose with a flattened bridge, and an enlarged tongue. For this reason, unrelated children with Hunter syndrome often look alike.

Effects Of MPS2

Clinically speaking, Hunter syndrome is inherited as an X-linked recessive disorder. History shows that the effects of this disease take a devastating toll on the child’s developmental and cognitive ability to live a fruitful, healthy life. Sadly enough, children diagnosed with most severe cases of Hunter’s syndrome, represent more than two thirds of all reported cases.

The onsets of Hunter’s symptoms are usually seen between 2 and 4 years of age. It is difficult to detect MPS2, because most symptoms are that of common childhood sicknesses.  Most diagnoses come from the signs of developmental delay as children begin school.  Unfortunately it is the extensive rapid neurological degeneration that precedes and ultimately causes death in children with the severe form of Hunter syndrome.

Children with severe Hunter’s syndrome have multiple unexplained health issues. These include short stature, skeletal deformities, spine deterioration, joint stiffness, coarse/puffy facial features, developmental delays, mental retardation, unexpected seizures,  premature brain failure, respiratory system problems, heart disease, carpal tunnel syndrome, the inability to walk, and  recognize their surroundings usually before the age of 12, and loss of life by 15.

MPS2 also has a tendency to attack and enlarge the internal organs, mainly the liver and spleen which can interfere with eating and breathing.

Potty training is a neurological function affected by MPS2/ Hunters, so training is almost impossible.  As a consequence of the nervous system failure some boys experience loose stool or chronic diarrhea.  The inability to be trained is embarrassing, for the boys, frustrating, for both child and parents, and extremely costly.

Boys trying to cope with the issues of stomach extension usually have a hard time wearing proper fitting clothes.  It becomes increasingly difficult to find elastic waist pants as children grow out of the toddler stage.  Most articles of clothing need to be altered.

The continued storage of GAG in cells can lead to organs being affected in important ways.

  • The thickening of the heart valves along with the walls of the heart can result in progressive decline in cardiac function.
  • The walls of the airway may become thickened as well, leading to breathing problems while sleeping (obstructive airway disease). People with Hunter syndrome may also have limited lung capacity due to pulmonary involvement.
  •  As the liver and spleen grow larger with time, the belly may become distended, making hernias more noticeable.
  • All major joints (including the wrists, elbows, shoulders, hips, and knees) may be affected by Hunter syndrome, leading to joint stiffness and limited motion.  Progressive involvement of the finger and thumb joints results in decreased ability to pick up small objects. The effects on other joints, such as hips and knees, can make it increasingly difficult to walk normally.
  • If carpal tunnel syndrome develops, a further decrease in hand function can occur. The bones themselves may be affected, resulting in short stature.
  •  In addition, pebbly, ivory-colored skin lesions may be found on the upper arms and legs and upper back of some people with Hunter syndrome. The presence or absence of the skin lesions is not helpful, however, in predicting clinical severity in Hunter syndrome.
  • Finally, the storage of GAG in the brain can lead to delayed development with subsequent mental retardation.

Sadly enough … the devastating effects of the disease will take control over their little lives which usually result in their passing between 10 and 15 years of age.

Treating MPS2

There is no cure for MPS diseases, but there are ways of managing and treating the problems they cause, including enzyme replacement therapies.

Medication

Treatments such as enzyme replacement therapies, ERT, help make the disease more manageable for the body. On July 24, 2006, the FDA granted marketing approval for ELAPRASE (idursulfase), the first FDA approved enzyme replacement therapy for the treatment for MPS II, also known as Hunter syndrome.

ELAPRASE infusion therapy is administered to aid the rapid deterioration of the bodies of MPS II patients and maintain their current health conditions.

This treatment aims to supplement the enzymes that are present at low levels in the body.

Enzyme replacement therapy (ERT) can be an effective treatment for symptoms of MPS II that do not involve the skeletal system and central nervous system (the brain and spinal cord).

Elaprase (idursulfase) is the first prescription medication prescribed for the treatment of Hunter syndrome. Elaprase is a new molecular entity, which is an active ingredient never before marketed in the United States. Elaprase was designated as an orphan product by the FDA. Orphan products, such as Elaprase, are generally developed to treat rare diseases or conditions that affect fewer than 200,000 people in the United States. Hunter Syndrome is so rare, there are less than 350 known cases which are being treated in the United States today.

What is ELAPRASE?

ELAPRASE is an enzyme replacement therapy from Shire Human Genetic Therapies.  ELAPRASE is designed to replace iduronate-2-sulfatase (I2S), the enzyme that is deficient or absent in people with Hunter syndrome (Mucopolysaccharidoses-2) Unfortunately, ELAPRASE is a weekly lifelong infusion therapy, which means it is given intravenously (by IV) over a 4 hour span.

Some patients experience some types of allergic reactions to ELAPRASE (idursulfase) infusion, but doctors can help patients with these reactions by pre-medicating, or administering medication at the time of reaction.  (Jason was one of them). Patients with compromised respiratory function or acute respiratory disease may have a higher risk of a life-threatening reaction to ELAPRASE infusion and require additional monitoring throughout the infusion.

ELAPRASE Enzyme Replacement Therapy is considered the one of the World’s Most Expensive medical treatments out today, with an estimated cost reaching approximately $300,000 – $500,000 per patient, per year depending upon the plan participant’s weight.

The average wholesale price (AWP) of a single use vial of ELAPRASE is $3,285.00.  For each patient, this results in a projected cost of approximately $6,570.00 per week, per child.

For more information on the treatment, visit http://www.elaprase.com/.

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