Definition:
Morquio type B/MPS IV B is caused by a mutated gene that manufactures the enzyme, beta-galactosidase. This enzyme is needed to break down a specific type of sugar or mucopolysaccharides called keratan sulfate. This sugar is used to build connective tissues and bones in the body. Individuals affected with Morquio type B/MPS IV B have too many keratan sulfates in their system because the enzyme, beta-galactosidase, needed to break down keratan sulfate, is absent or present in only very small quantities. The excessive amounts of keratan sulfate lead to the clinical symptoms of Morquio type B/MPS IV B.

There are two forms of Morquio MPS IV, Type A and Type B. Type A is more common of the two forms. There is little difference in the clinical symptoms between both forms of the disorder and a wide range of symptoms associated with each form.

The incidence of both forms of Morquio MPS IV is estimated to be 1 in 200,000 live births worldwide.

Symptoms:
The wide range of symptoms for Morquio type B/MPS IV B have been classified into sections. Typically, symptoms begin to appear at around 18 months of age.

Skeletal Symptoms:
Skeletal symptoms appear at around 18 months of age, when growth also begins to decline. Children with a severe form of this disorder typically stop growing around eight years of age, their final height measuring between three and four feet.

Curvature of the spinal column leads to deformity of the chest Restricted breathing as well as serious chest and lung infections are consequences of this chest deformation. Other bone abnormalities such as dislocated hips or shoulders, knock-knees, weak wrists, loose joints, scoliosis and an unstable neck, leading to nerve damage or paralysis, are common symptoms of this disorder.

Facial Symptoms:
A short neck, wide mouth, enlarged tongue, poorly formed teeth and flattened nose bridges are some of the facial characteristics of children affected with Morquio type B/MPS IV B.

Neurological Symptoms:
Corneal clouding and hearing loss are two neurological symptoms associated with this disorder.

Organ damage:
Leaky or blocked heart valves and heart murmurs are symptoms of thisdisorder, as are hernias and/or an enlarged liver and spleen.

Inheritance Pattern:
Morquio type B/MPS IV B is an autosomal recessive disorder.

Life Expectancy:
Life expectancy for individuals afflicted with mild Morquio type B/MPS IV B is 60 years of age. The life expectancy for individuals affected with severe Morquio type B/MPS IV B is 30 years of age or younger.

Diagnosis and Testing:
A urine test may determine whether an individual has Morquio type B/MPS IV B. The test measures increased levels mucopolysaccharides, the type of sugar chain in the lysosome that accumulate as a result of the malfunctioning enzyme. A urine test is routinely followed by a blood test or skin biopsy, which will reveal reduced activity of the enzyme beta-galactosidase. Prenatal screening is available to examine beta-galactosidase activity in the fetus. Genetic testing is also available in combination with these diagnostic tests to look for the mutation that causes Morquio type B/MPS IV B.

Treatment:
There is no cure for Morquio type B/MPS IV B. In most cases, treatment is limited to reducing or controlling the symptoms of this disorder by consulting on a regular basis with neurologists, ophthalmologists, orthopedists, cardiologists and genetic counselors. Although a diet low in sugar does not reduce the levels of mucopolysaccharides in the body, some parents avoid certain foods like sugar and artificial additives that may increase hyperactivity. Dairy products may also be avoided to reduce the amount of mucus production or if diarrhea is present. Exercise is highly encouraged to maintain muscle strength, along with maintaining proper dental hygiene practices to reduce further tooth decay.

Medications to reduce joint pain and antibiotics to treat pulmonary infections are prescribed as needed.

A cervical spine fusion is may result in control of the unstable neck that is characteristic of this disorder. Hip and/or knee replacement surgery may also be necessary. A back brace may slow the progression of scoliosis and delay the necessity of back surgery.

Bone marrow transplants have been used as possible treatment option but have not proven effective at reducing the progression of this disorder or halting its course. Enzyme replacement therapy is being researched as a possible cure in the future.

Patient Groups:
National MPS Society
4220 NC Highway 55, Suite 140
Durham NC, 27713
www.mpssociety.org
tel: (919) 806-0101
fax: (919) 806-2005
Barbara Wedehase, Executive Director
info@mpssociety.org