Disease: Hunter syndrome


    Hunter syndrome is a very rare, inherited genetic disorder caused by a missing or malfunctioning enzyme. Because the body doesn't have enough of the enzyme to break down certain complex molecules, the molecules build up in harmful amounts.

    In Hunter syndrome, the buildup of massive amounts of these harmful substances 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 mainly occurs in boys, although very rarely it has been observed in girls.

    There's no cure for Hunter syndrome. Treatment of Hunter syndrome involves management of symptoms and complications.

    Source: http://www.mayoclinic.com


    Hunter syndrome is one type of a group of inherited metabolic disorders called mucopolysaccharidoses (MPSs), and Hunter syndrome is referred to as MPS II.

    Hunter syndrome symptoms vary and range from mild to severe. Symptoms aren't present at birth, but often begin around ages 2 to 4.

    Signs and symptoms may include:

    • An enlarged head (macrocephaly)
    • Thickening of the lips
    • A broad nose and flared nostrils
    • A protruding tongue
    • A deep, hoarse voice
    • Abnormal bone size or shape and other skeletal irregularities
    • A distended abdomen, as a result of enlarged internal organs
    • Diarrhea
    • White skin growths that resemble pebbles
    • Joint stiffness
    • Aggressive behavior
    • Stunted growth
    • Delayed development, such as late walking or talking

    When to see a doctor

    Hunter syndrome is very uncommon, but if you notice changes in your child's facial appearance, a loss of previously acquired skills, or other signs or symptoms listed above, talk to your child's primary care doctor. He or she can help you decide if you need to see a specialist or seek further testing.

    Source: http://www.mayoclinic.com


    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 sugar molecules is missing or malfunctioning.

    Without this enzyme, massive amounts of these complex sugar molecules collect in the cells, blood and connective tissues, causing permanent and progressive damage.

    Source: http://www.mayoclinic.com


    Babies born with Hunter syndrome almost always appear healthy at birth. Changes in facial features are often the first noticeable sign that something's not right.

    Blood, urine or tissue samples can be checked for the deficient enzyme or for excess amounts of the complex sugar molecules associated with this disorder. A genetic analysis can confirm the diagnosis.

    Because Hunter syndrome progresses slowly and its signs and symptoms overlap with a number of other disorders, definitive diagnosis may take some time.

    Prenatal testing

    Prenatal testing of the fluid that surrounds the baby (amniocentesis) or of a tissue sample from the placenta (chorionic villus sampling) can verify if your unborn child carries a copy of the defective gene or is affected with the disorder.

    Source: http://www.mayoclinic.com


    A variety of complications can occur with Hunter syndrome depending on the type and severity of the disease. Complications can affect the lungs, heart, joints, connective tissue, and brain and nervous system.

    Respiratory complications

    An enlarged tongue, thickened gums, and thickening of the nasal passages and windpipe (trachea) make breathing difficult. Children often have chronic ear and sinus infections, respiratory infections, and pneumonia.

    Sleep apnea, a condition in which breathing is intermittently interrupted during sleep, is often present because of airway constriction.

    Cardiac complications

    Thickening of heart tissue can cause improper closing of heart valves. As a result, the heart and other parts of the body don't receive blood efficiently. As the disease progresses, these conditions often become worse and typically result in heart failure.

    The thickening of tissue can also cause narrowing of the aorta (coarctation) and other blood vessels. This in turn can result in high blood pressure (hypertension) and narrowing of arteries in the lungs (pulmonary hypertension).

    Skeletal and connective tissue complications

    The storage of undigested complex sugar molecules in connective tissues results in abnormalities in bones, joints and ligaments. This reduces your child's growth, causing pain and physical malformations and making it difficult for him or her to move.

    Joint stiffness is caused by swelling of joint connective tissues and abnormalities of cartilage and bones. If your child is in pain, he or she will likely move less, which can lead to more stiffness and pain.

    The group of abnormalities typically seen in the bones of people with Hunter syndrome is called dysostosis multiplex. Children with these abnormalities can develop irregularly shaped vertebrae and spines (kyphoscoliosis), ribs, arms, fingers, legs, and pelvises.

    Their skulls may press down on or fuse with their upper spines. These complications cause many people with Hunter syndrome to be abnormally short. Those with milder cases may reach normal or near-normal height.

    Hernias (inguinal and umbilical) are common in Hunter syndrome. A hernia occurs when soft tissue, usually part of the intestine, pokes through a weak spot or tear in the lower abdominal wall.

    Hernias associated with Hunter syndrome can become quite large and are often one of the first signs of the disorder. Enlargement of the liver and spleen (hepatosplenomegaly) may increase pressure in the abdomen, causing a hernia.

    Brain and nervous system complications

    A variety of neurological complications may be present and continue to develop in children with Hunter syndrome.

    Many neurological problems are caused by buildup of excess fluids in your child's brain (hydrocephalus). Pressure from these fluids can cause other problems that may affect your child's eyes, ears and other sensory organs, which can cause severe headaches, interfere with vision or hearing and change your child's mental state.

    Your child also may develop a condition in which the membranes that surround the spinal cord may become thick and scarred (hypertrophic cervical pachymeningitis). This causes pressure and compression of the upper spinal cord. As a result, your child may develop fatigue in his or her legs and gradually weaken and become less physically active.

    Other disorders, such as carpal tunnel syndrome, can result from nerve compression that happens because of bone deformities and storage of complex sugar molecules in tissues.

    Abnormal behavior can develop in children with more-severe cases of Hunter syndrome. Often your child's mental development will become affected between the ages of 2 and 6. Some children are hyperactive and have trouble paying attention or following directions. Your child may also behave aggressively and seem unable to sense danger. As your child's overall physical functioning declines, these behavior problems tend to become less severe.

    Seizures also may occur in children with Hunter syndrome.

    Longer recovery from other illnesses

    Recovery times from normal childhood illnesses may be longer for children with Hunter syndrome. As a result, be sure to take general preventive measures — for example, get your child a flu shot and ensure your child receives all necessary vaccinations.

    Source: http://www.mayoclinic.com


    Hunter syndrome is a genetic disorder. Talk to your doctor or a genetic counselor if you're thinking about having children and you or any members of your family have a genetic disorder or a family history of genetic disorders.

    If you think you might be a carrier, genetic tests are available. If you already have a child with Hunter syndrome, you may wish to seek the advice of a doctor or genetic counselor before you have more children.

    Source: http://www.mayoclinic.com

    Coping and support

    Joining a support group for parents of children with Hunter syndrome can be a great way to obtain practical information, daily living strategies and encouragement from other parents in similar situations to your own. Ask your doctor if there's a group in your area.

    The intense supervision that may be needed for your child can cause you and other caregivers to become physically, mentally and emotionally exhausted. If respite care is available, take advantage of it so that you can have a break and be more effective in the long run to meet the day-to-day challenges of caring for your child.

    Check with your county and state for resources that may be available to you as a parent of a child with special needs.

    Letting others know

    Due to a narrow airway, people with Hunter syndrome often have difficulty receiving a breathing tube (being intubated) during general anesthesia. You may wish to note this on child care or school forms so that emergency personnel can be alerted to this fact, in case your child has an emergency and you're not there. An experienced anesthesia specialist (anesthesiologist) should perform the intubation of a person with Hunter syndrome.

    Source: http://www.mayoclinic.com

    Risk factors

    There are two major risk factors for developing Hunter syndrome:

    • Family history. Hunter syndrome is caused by a defective chromosome, and a child must inherit the defective chromosome to develop the disease. Hunter syndrome is what's known as an X-linked recessive disease. This means that women carry the defective disease-causing X chromosome and can pass it on, but women aren't affected by the disease themselves.
    • Sex. Hunter syndrome nearly always occurs in males. Girls are far less at risk of developing this disease because they inherit two X chromosomes. If one of the X chromosomes is defective, their normal X chromosome can provide a functioning gene. If the X chromosome of a male is defective, however, there isn't another normal X chromosome to compensate for the problem.

    Source: http://www.mayoclinic.com

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