Estimated occurrence1 in 100,000 live births.
Hunter syndrome is a metabolic disease belonging to the group of mucopolysaccharidoses. The syndrome has X-linked recessive inheritance (Xq27-28) and is caused by a mutation of the gene that controls the formation of the enzyme iduronate sulfatase. A shortage of iduronate sulfatase leads to an accumulation of mucopolysaccharides in cells.
Several organs may be affected by the syndrome, including the brain, heart, joints, bones, respiratory organs, the gastro-intestinal system and the liver. Hearing impairment is common and visual impairment may occur. Growth in height is often stunted. There is an increased risk of developing hydrocephalus. There are large individual variations and the degree of severity varies. Many, but not all, suffer from neurological/neuropsychiatric symptoms and intellectual disabilities. Onset of the symptoms starts at 2 to 4 years of age and they gradually become more severe.
Mucopolysaccharidosis type II, MPS II, Iduronate sulfatase deficiency.
Boys with Hunter syndrome develop a distinctive appearance. Coarse facial features and an enlarged tongue are common. Gums may also be enlarged. Teeth are often widely spaced and many have open bites. Breathing difficulties are common and may be exacerbated by narrow air passages caused by mid-facial underdevelopment, enlarged tonsils, polyps and mucus formation. Upper respiratory infections, pneumonia and sleep apnoea are common. Oral motor control is often affected, which can limit the ability to speak, eat and control saliva. Most boys with neurological symptoms have communication difficulties.
Advice on follow-up and treatment
- Early contact with dental services for intensified prophylactic care and oral hygiene information is essential.
- Regular check-ups of dental and jaw development. Orthodontist should be consulted when needed.
- Training in oral motor skills and extra stimulation in cases of eating disorders, speech difficulties and impaired saliva control may be necessary.
- Communication training is often warranted.
- Feeding and swallowing difficulties are investigated and treated by a specialist team at the hospital or multidisciplinary treatment centre.
- When treating medically compromised patients always contact their doctor for medical advice (bleeding problems, heart diseases etc).
- Patients with MPS syndromes should be examined by an experienced anaesthetist before planned surgery.