Alternative Treatment For Hunter Syndrome
Hunter syndrome is also known as mucopolysaccharidosis type II. Hunter syndrome is a disease caused by deficiency of an enzyme named iduronate-2-sulfatase (I2S), which is a lysosomal enzyme. It is an X-linked recessive disease. Due to deficiency of iduronate-2-sulfatase, there is accumulation of dermatan sulfate and heparin sulfate (both are types of mucopolysaccharides) in the body tissues and this causes abnormalities in the major organs like heart, central nervous system and respiratory system.
Alternative Treatment For Hunter Syndrome
Hunter syndrome is a non-curable disease. There are few emerging alternative treatment options for this disease-
Enzyme Replacement Therapy (ERT)
A purified form of the enzyme iduronate-2-sulfatase that is absent in this disease is available as idursulfase and this can be used to reduce the severity of Hunter syndrome. Administering this drug into the body of patient can be helpful to breakdown the mucopolysaccharides. But this enzyme cannot cross the blood brain barrier that covers the brain and so if the disease is severe and affects the brain, this treatment method will not be very useful. (1) (2)
After administration of ERT the patient’s urinary GAG excretion levels must be monitored. Also the weight of the patient must be kept in check to adjust the dose accordingly. Usually ERT is given in the dose of 0.5 mg/kg per week. Chances are there that ERT might cause reactions. Two types of reactions can occur, one that occurs at the time of infusion and other occurs after 12 hours of infusion. The immediate reaction presents as chills, fever and urticaria. When these signs are seen, the infusion must be stopped promptly and antihistamines must be administered. The infusion can be restarted after 30 minutes. To prevent the chances of reaction, the medical health worker can premedicate the patient with antihistamines or acetaminophen.
When the reaction occurs after 12 hours of infusion, the presenting signs are rash and wheezing. The rash can be treated with corticosteroids, antihistamines or acetaminophen. If wheeze is present, it can be treated with the help of oxygen supplementation or bronchodilators or both.
Anti-inflammatory Drugs- Using anti-inflammatory drugs helps to reduce the severity of inflammation and helps in improving the quality of life of the patient.
Hematopoietic Stem Cell Transplantation (HSCT)- In HSCT, the donation can be of cord blood, bone marrow or peripheral blood stem cells from the healthy donor. But it was found that patients who were treated with HSCT had high mortality rate.
Gene Editing Therapy- This is the most recent advancement for treating hunter syndrome. It permanently alters the DNA of the patient by editing the diseased chromosome with normal one.
Other Types Of Mucopolysaccharidosis
Mucopolysaccharidosis Type I (MPS I)-
On the basis of severity of the disease MPS I, it can be divided into three subtypes- Hurler syndrome, Scheie syndrome and Hurler-Scheie syndrome. Hurler and Scheie syndromes are the two extremities of the disease and Hurler-Scheie syndrome falls in between the two.
MPS I is caused due to deficiency of alpha-L-iduronidase. The three subtypes are differentiated on the basis of clinical symptoms and severity. Hurler syndrome (MPS 1-H) is a multisystem disease and it results in early death of the child. It is diagnosed at the age of 4 to 18 months.
Scheie syndrome is the mildest amongst all the types of mucoploysaccharidosis. The symptoms of this type are seen after the age of five years. The children suffering from this disease usually have normal intelligence, normal growth and stature and good life expectancy. The symptoms include- carpal tunnel syndrome, painful joints, glaucoma and aortic valve disease.
Hurler-Scheie Syndrome (MPS I H/S)-
It is an intermediate type of disease. It is neither severe nor mild. There is little or no abnormality related to intellectual capacity. The symptoms appear between the ages of three to eight years. The symptoms include, corneal clouding, coarse facial features, short stature, joint stiffness and hepatosplenomegaly. The patient can survive up to adulthood.
Mucopolysaccharidosis type 3- also called as Sanfilippo syndrome
Mucopolysaccharidosis type 4- also called as Morquio syndrome
Mucopolysaccharidosis type 6- also called as Maroteaux-Lamy syndrome
Mucopolysaccharidosis type 7- also known as Sly syndrome
Mucopolysaccharidosis type 9- also known as Hyaluronidase deficiency
The alternative treatment options for hunter syndrome are Enzyme Replacement Therapy (ERT), anti-inflammatory drugs, Hematopoietic Stem Cell Transplantation (HSCT) and gene editing therapy.
Enzyme Replacement Therapy (ERT) for hunter syndrome includes treatment with idursulfase. Anti-inflammatory drugs like corticosteroids are used to reduce the intensity of inflammation. HSCT is not a preferred option because it has been found that it increases chances of mortality. Also, graft versus host reactions are also noted in the patients. Along with all this, social support and familial support is very necessary for betterment of the patient.