InternationalResearch and clinical trials
In Hunter syndrome, siblings who started enzyme therapy in infancy did better
Records of 19 sibling pairs with Hunter syndrome were compared.
Peer-reviewed publicationMPS II
Lysosomal storage diseases
Hunter syndrome (MPS II)
A lysosomal storage disease. Because of an enzyme deficiency, substances build up in many organs. It is seen mostly in boys.
Not part of the panel of Türkiye's National Newborn Screening Programme (heel-prick test). Source
This page is translated from the Turkish original.
This disease is followed through the “Lysosomal storage diseases” group.
Understanding the disease
This section has not yet been reviewed by a physician. It summarises patient information from sources such as MedlinePlus, Orphanet and the NHS in plain language. The disease can differ from person to person; talk to your doctor about diagnosis and treatment.
What happens in this disease?
The body lacks an enzyme that breaks down sugar molecules called GAGs (glycosaminoglycans). GAGs build up in cells and affect many organs. In the severe type, the disease progresses quickly and shortens life. In the mild type, intelligence is not affected; people often reach adulthood.
Which symptoms can occur?
Babies look healthy at birth. Symptoms often begin between 2-4 years of age and increase over time.
- Frequent infections, hernias and digestive problems (among the early symptoms)
- Coarsening of facial features, a large tongue and a deep voice
- Large head, liver and spleen
- Narrowing of the airway; pauses in breathing during sleep (sleep apnea)
- Hearing loss
- Joint stiffness, bone differences and short stature
- Heart valve problems
- Decline in mental abilities in the severe type
How is it diagnosed?
A high level of GAGs in the urine suggests the diagnosis. The diagnosis is confirmed by showing the enzyme deficiency in the blood. A genetic test finds the change in the gene.
Treatment and care
One option is enzyme replacement therapy (giving the missing enzyme into a vein). Surgery, heart care and bone care may also be needed. Regular check-ups and comfort (palliative) support are part of care. The doctor who follows the disease decides which treatment is suitable.
For the family: inheritance and genetic counselling
The disease is passed on through the X chromosome, so it occurs almost always in males. For each son of a carrier mother, the chance of being affected is 1 in 2. Carrier testing and genetic counselling are recommended for women in the family.
Source: MedlinePlus Genetics — Mucopolysaccharidosis type II · Orphanet — Mucopolysaccharidosis type 2
Key facts
- How common is it?
- Prevalence: 1-9 per 1 000 000 (Europe) · Birth prevalence: 1-9 per 1 000 000 (Worldwide)
- How is it inherited?
- X-linked recessive
- When does it usually start?
- Childhood
- Gene(s) involved
- IDS
- Reliable sources
- MedlinePlus (for families) · Orphanet · GeneReviews (for doctors)
These facts are taken from Orphanet and MedlinePlus records (last checked: October 7, 2026). Frequency values are approximate ranges.
You are not alone: patient associations in Türkiye
Non-profit patient and family organizations in Türkiye working on this disease or disease group. Links are for information; Doktorclub is not affiliated with these organizations and does not endorse them.
- Mukopolisakkaridoz ve Benzeri Lizozomal Depo Hastalıkları Derneği · Specific to this disease · İstanbul
For all rare diseases: Nadir Hastalıklar Federasyonu
Links checked on October 8, 2026.
Support and help
- In an emergency in Türkiye, call 112.
- For psychological and social support, the ALO 183 Social Support Line (24/7, free from within Türkiye): alo183.aile.gov.tr
- For carers: Looking after yourself as a caregiver
- Preparing for a doctor visit · Collect your questions and symptom notes on one page, then print it and take it with you.
Doktorclub does not diagnose, recommend treatments or refer you to hospitals or doctors. These pages are meant to help you talk with your doctor.
News about MPS II
USANew treatments and approvals
Accelerated approval for tividenofusp alfa for nervous system features of Hunter syndrome
Through the accelerated pathway, the FDA has approved tividenofusp alfa for children with Hunter syndrome (MPS II).
Official drug approvalMPS II
Clinical trials (ClinicalTrials.gov)
A clinical trial is a regulated study that tests whether a new treatment is safe and whether it works, in patients who volunteer. Most trials look for a certain age, genetic change and health condition. Taking part is voluntary.
This list is not a treatment recommendation. Treatments tested in phase 1–3 trials are investigational (experimental): their efficacy and safety have not yet been proven and they are not approved treatments. Taking part depends on each trial’s criteria and a physician’s assessment; the first step is to talk to the doctor who manages your care.
Questions you can ask your doctor
- Could this trial be suitable for us?
- If we take part, how would current treatment and check-ups be affected?
- Where does the trial take place, and how are travel and accommodation handled?
- What happens if we want to leave the trial?
ClinicalTrials.gov lists 17 active interventional studies for this disease. 2 are recruiting now; 3 have sites in Türkiye. Last checked: October 7, 2026.
Selected records (studies with a site in Türkiye first):
- A Phase III Study of JR-141 in Patients With Mucopolysaccharidosis II (STARLIGHT)
Late stage: the effect is being compared in a large group · Phase 3 · investigational (experimental)Active, not recruitingSite in TürkiyeNCT04573023
- UCB Transplant of Inherited Metabolic Diseases With Administration of Intrathecal UCB Derived Oligodendrocyte-Like Cells
Early stage: safety and dose are being tested · Phase 1 · investigational (experimental)RecruitingNCT02254863
- PEARL (PrEnAtal Enzyme Replacement Therapy for Lysosomal Storage Disorders)
Early stage: safety and dose are being tested · Phase 1 · investigational (experimental)RecruitingNCT04532047
- A Multi-cohort Study of Safety, Efficacy, PK and PD of GNR-055 in Patients With Mucopolysaccharidosis Type II
Late stage: the effect is being compared in a large group · Phase 2 / Phase 3 · investigational (experimental)Active, not recruitingNCT05208281
- An Extension Study of JR-141-BR21 in Patients With Mucopolysaccharidosis II
Middle stage: the effect is being tested in a small group · Phase 2 · investigational (experimental)Active, not recruitingNCT03708965
See all studies on ClinicalTrials.gov · Joining clinical trials
Lysosomal storage diseases: other news
USANew treatments and approvals
Rebisufligene etisparvovec receives FDA approval as first treatment for Sanfilippo type A
The FDA has approved rebisufligene etisparvovec for children with Sanfilippo syndrome type A (MPS IIIA).
Official drug approvalMPS IIIA
ChinaResearch and clinical trials
Gene therapy tested in 6 children with infantile-onset Pompe disease
In China, 6 children with infantile-onset Pompe disease were given a single dose of gene therapy.
Peer-reviewed publicationPompe
TürkiyeDiagnosis and screening
Fabry screening of dialysis patients in Ankara: one patient led to 6 carriers in the family
In Ankara, 1,359 patients at 8 dialysis centers had a gene test for Fabry disease.
Peer-reviewed publicationFabry
Medical codes (for talking with your doctor and finding sources)
These codes identify the disease in international classifications and databases. They can help when you talk with your doctor or look for reliable sources.
Orphanet code: ORPHA:580 · ICD-11 5C56.31
Codes checked against WHO ICD-11 and Orphanet on October 6, 2026.
This page provides general information and does not replace diagnosis or treatment. Talk to your doctor about symptoms, diagnosis and treatment.