It is a rare X-linked lysosomal storage disorder caused by the deficiency of iduronate-2-sulfatase (IDS).
About Hunter Syndrome
What is
Hunter Syndrome?
Hunter syndrome is Mucopolysaccharidosis type II (MPS II). It takes its name from Charles Hunter (1873-1955) who first described two brothers with the disease in 1917. MPS II is a rare X-linked lysosomal storage disorder caused by the deficiency of iduronate-2-sulfatase (IDS).
In affected patients, glycosaminoglycan (GAG) accumulates in the lysosomes of many organs and tissues contributing to the pathology associated with MPS II.
Patients are categorized according to the presence (neuronopathic MPS II) or absence (attenuated MPS II) of CNS involvement, with approximately two-thirds of patients having neuronopathic MPS II.
The treatment of MPS II was palliative prior to the introduction of enzyme replacement therapy (ERT).
In affected patients, glycosaminoglycan (GAG) accumulates in the lysosomes of many organs and tissues contributing to the pathology associated with MPS II.
Patients are categorized according to the presence (neuronopathic MPS II) or absence (attenuated MPS II) of CNS involvement, with approximately two-thirds of patients having neuronopathic MPS II.
The treatment of MPS II was palliative prior to the introduction of enzyme replacement therapy (ERT).
Signs & Symptoms
In patients with the severe form, the onset of clinical symptoms is usually presented between 2 and 4 years of age,
with progressive neurologic symptoms leading to cognitive impairment. In exceptional cases, children with a family history may be diagnosed before disease onset.
The Phase I/II studies of Hunterase suggest the importance of early initiation of ERT because of the irreversible nature of CNS disease.
with progressive neurologic symptoms leading to cognitive impairment. In exceptional cases, children with a family history may be diagnosed before disease onset.
The Phase I/II studies of Hunterase suggest the importance of early initiation of ERT because of the irreversible nature of CNS disease.
Non-neuronopathic (attenuated) type: Minimal CNS involvement
Common symptoms & signs
Developmental delay
Coarse face
Short stature
Skeletal abnormalities
(dysostosis multiplex)
Coarse face
Short stature
Skeletal abnormalities
(dysostosis multiplex)
Joint contracture
Hepatosplenomegaly
Upper airway obstruction
Valvular heart disease
Hepatosplenomegaly
Upper airway obstruction
Valvular heart disease
Neuronopathic (severe) type: CNS involvement
Neurobehavioral symptoms
Aggression
Hyperactivity
Sleep disturbances
Progressive neurological decline
Cognitive impairment
Hyperactivity
Sleep disturbances
Progressive neurological decline
Cognitive impairment
Diagnosis
Diagnostic Algorithm for Hunter Syndrome
Genetic Disease
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome and in females who are homozygous for the gene mutation. Females with one copy of the mutated gene are carriers.
In the case of MPS II (Hunter syndrome), mutations in the IDS gene located at Xq28 are responsible for the disease.
In the case of MPS II (Hunter syndrome), mutations in the IDS gene located at Xq28 are responsible for the disease.
Hunter Syndrome Inheritance
If mother has one copy of the mutated gene,
- A 50% (1 in 2) chance a boy will be affected
- A 50% (1 in 2) chance a girl will be a carrier
Father
Unaffected
Mother
Carrier
Boy
Unaffected
Boy
Affected
50%
Girl
Unaffected
Girl
Carrier
50%
If father is affected with Hunter syndrome,
- A 100% chance a boy will be unaffected
- A 100% chance a girl will be a carrier
Father
Affected
Mother
Unaffected
Boy
Unaffected
Boy
Unaffected
Girl
Carrier
100%
Girl
Carrier
100%
References
- Orphanet J Rare Dis. 2013;8:42
- Mol Ther Methods Clin Dev. 2021;21:67-75
- Mol Genet Metab. 2015;114(2):156-60
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