A variety of complications can occur with Hunter syndrome depending on the type and severity of the disease. These may include:
- Respiratory complications. All forms of MPS, including Hunter syndrome, involve respiratory complications that contribute to your child's disability and sometimes cause death as the disease progresses. 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 tissue associated with Hunter syndrome can cause progressive thickening of the heart's valves. This causes 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 glycosaminoglycans 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.
Nearly everyone with Hunter syndrome experiences joint stiffness, which makes movement painful. The 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. They happen because of problems with connective tissue. 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), which is common in Hunter syndrome, 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 and other sensory organs, which can cause severe headaches, interfere with vision and change your child's mental state. Placement of a shunt may help drain excess fluids and relieve pressure on the spinal cord. Imaging tests also may reveal a variety of cyst-like structures in parts of the brain.
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 glycosaminoglycans 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. Be aware that recovery times from normal childhood illnesses may be longer for children with Hunter and other MPS syndromes. 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.