Hunter Syndrome-Type A

In this type of mucopolysaccharidosis, the condition is sex-linked, and, therefore, it is always a male who inherits the disease from his mother, either through a mutation in her X-chromosome or through an abnormal X-chromosome inherited by her from an earlier generation.

The skeletal features of dwarfism and joint deformities are similar to those of mucopolysaccharidosis I-H (Hurler’s Syndrome) but less marked. Spine deformity is less marked and acute kyphosis does not usually develop.

Hepatosplenomegaly is present but corneal clouding and opacities do not develop and mental retardation is minimal and occurs late.

Heparan sulphate is the main glycosaminoglycan excreted in the urine, with lesser amounts of dermatan sulphate. The casual enzymatic defect is a sulpho-iduronate sulphatase.

Radiological Appearance

The bony changes are generally like those in Hurler’s syndrome but usually less severe. Many patients do not have a kyphos, or a beaked, notch or hooked vertebra and the pelvic changes are less marked, but there is a spectrum of abnormality that may approach the degree of bony change in Hurler’s syndrome. In older patients, irregularity of the bones of the hip predisposes to early osteoarthritis.

Differential Diagnosis

Absence of corneal clouding, normal intelligence, less severe defects and absence of affected females suggests a diagnosis of Hunter’s from Hurler’s syndrome. In an equivocal case, fibroblast culture and biochemical assessment may be needed to make the diagnosis certain.

Treatment
In severe cases with extensive visceral manifestations, surgery has little to offer but in patients with the probability of survival into adolescence, deformities that interfere with daily management may deserve correction by osteotomy.

Related posts:

1. Hunter Syndrome II B-Mild Type
2. Hurler Syndrome
3. Mucopolysaccharidosis IV or Morquio Syndrome
4. Dignosis And Treatment of Klippel-Feil syndrome
5. Klippel-Feil Syndrome-Overview and Clinical Presentation