Hunters syndrome is an inherited disorder whereby the enzyme iduronate-2-sulfatase (I2S) tends to be deficient. This enzyme is involved in the breakdown of complex carbohydrates known as mucopolysaccharides. When enough I2S is not broken down, mucopolysaccharides accumulate in the body's organs, and tissues hence become toxic. Hunters syndrome is an X-linked disorder that is transmitted on the X chromosome from the mother to a child. Due to this, the hunters syndrome orphan diseases are often found in male children, but very few female cases have been reported. There are two types of hunters syndrome; type A and type B.
Symptoms of hunters syndrome orphan diseases
Usually occurs in children between 18 to 36 months of age. It is a severe form of hunters syndrome and is also called the classic form. Children with this type of orphan diseases may survive to the second and third decades of life. Its symptoms include:
- Enlarged liver and spleen
- Skeletal changes, joint stiffness, short neck, large head and broad chest.
- Coarse facial features and short stature
- Progressive and profound mental retardation
- Progressive deafness
- Ivory colored skin lesions on the upper back and sides of the uppers thighs and arms
- Typical retinitis pigmentosa and visual impairment.
- Broad nose and flared nostrils
- Claw like hands
- Protruding tongue
- Aggressive behavior
Type B is much milder than type A and may remain unnoticed until adulthood. Individuals suffering form this orphan diseases may live till their 70's. A person with type B often has normal intelligence and lacks the severe skeletal problems experienced in type A. Its symptoms include:
- Abnormal bone size or shape and skeletal irregularities that are less severe than in type A
- Stunted growth
- Poor peripheral vision
- Joint stiffness
- Loss of hearing ability
- Sleep apnea
- Carpal tunnel syndrome
Diagnosis of hunters syndrome orphan diseases
The main diagnosis of hunters syndrome orphan diseases is a change in and on the body, like ivory colored skin lesions, spleen and liver enlargement in type A. Type B is hard to recognize by just looking at a person’s body.
The diagnoses from these changes are confirmed by;
A blood test for the deficiency of I2S.
A urine test may also be conducted to look for mucopolysaccharides presence in urine which suggests hunters syndrome.
X-rays can also reveal bone structural changes that are characterized with hunters syndrome orphan diseases.
Treatment of hunters syndrome orphan diseases
Due to the nature of the disease, there is no proven treatment yet but there ways to prevent the symptoms from becoming severe.
- Palliative treatment: this treatment is used to reduce the effects of deterioration of many bodily functions. Surgery and psychiatry are often handy in this treatment.
- Bone marrow graft: it is the most commonly used treatment. This treatment has a way of procuring a new source of the lacking I2S. The treatment is able to stop a significant number of symptoms and increases life expectancy but is inefficient against brain symptoms of the hunters syndrome orphan diseases.
- Elaprase: it is a purified form of lysosomal enzyme iduronate-2-sulfatase that is produced by recombinant DNA technology in the human cell line. It is considered an advance treatment that has all the advantages of bone marrow grafts. This treatment can cause hypersensitivity reactions.