From the Guidelines
Hunter Russell syndrome, also known as Hunter syndrome or mucopolysaccharidosis type II (MPS II), is a rare genetic disorder caused by a deficiency of the enzyme iduronate-2-sulfatase, which leads to the accumulation of glycosaminoglycans in various tissues and organs. This X-linked recessive condition primarily affects males and is characterized by progressive multisystem involvement. Patients typically present with:
- Coarse facial features
- Skeletal abnormalities
- Joint stiffness
- Hearing loss
- Cardiac problems
- Respiratory issues
- In severe cases, cognitive impairment Treatment involves enzyme replacement therapy with idursulfase (Elaprase), administered intravenously at 0.5 mg/kg weekly, which helps manage somatic symptoms but does not cross the blood-brain barrier to address neurological manifestations, as reported in a systematic evidence review 1. Supportive care is essential and may include:
- Physical therapy
- Occupational therapy
- Hearing aids
- Cardiac monitoring
- Respiratory support Early diagnosis and intervention are crucial for better outcomes, as emphasized in a study on the treatment of mucopolysaccharidosis type II (Hunter syndrome) 1. The condition results from mutations in the IDS gene on the X chromosome, leading to the enzyme deficiency that disrupts the normal breakdown of certain complex carbohydrates, causing their harmful buildup throughout the body, as discussed in a review of the treatment of MPS II 1. The most effective treatment approach is enzyme replacement therapy with idursulfase, which has been shown to reduce urinary glycosaminoglycan levels by a weighted average of 61%, as reported in a study on the efficacy of idursulfase in patients with MPS II 1. Overall, a comprehensive treatment plan that includes enzyme replacement therapy and supportive care can help manage the symptoms of Hunter Russell syndrome and improve patient outcomes, as supported by the evidence from recent studies 1.
From the Research
Definition and Overview of Hunter Syndrome
- Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II), is a rare X-linked lysosomal storage disorder caused by a deficiency of the enzyme iduronate-2-sulfatase (I2S) 2, 3, 4, 5, 6.
- This deficiency results in the accumulation of glycosaminoglycans (GAGs) in various tissues and organs, leading to multisystem organ failure and early death 3, 6.
Clinical Manifestations
- Clinical manifestations of Hunter syndrome vary widely in severity and involve multiple organs and tissues, including neurological abnormalities, severe airways obstruction, skeletal deformities, and cardiomyopathy 2, 3, 5, 6.
- Common signs and symptoms include inguinal hernia, frequent ear and respiratory infections, facial dysmorphisms, macrocephaly, bone dysplasia, short stature, sleep apnea, and behavior problems 2.
Diagnosis and Treatment
- Diagnosis is based on screening urinary glycosaminoglycans and confirmation by measuring I2S activity and analyzing I2S gene mutations 2.
- Enzyme replacement therapy (ERT) with idursulfase is a commercially available treatment that has been shown to improve walking capacity and respiratory function, reduce spleen and liver size, and decrease urinary glycosaminoglycan levels 2, 3, 4, 5, 6.
- ERT has been found to be generally well-tolerated, although infusion reactions can occur, and idursulfase antibodies have been detected in some patients 3, 6.
Research and Evidence
- Studies have demonstrated the effectiveness of ERT with idursulfase in improving functional capacity, reducing liver and spleen volumes, and decreasing urine glycosaminoglycan excretion in patients with Hunter syndrome 3, 4, 5, 6.
- However, more research is needed to obtain information on the long-term effectiveness and safety of ERT, as well as its impact on outcomes such as growth, sleep apnea, cardiac function, quality of life, and mortality 6.