Definition:
Morquio type A/MPS IV A is caused by a mutated gene that manufactures the enzyme, N-acetylgalactosamine 6-sulfatase. 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 A/MPS IV A have too many keratan sulfates in their system because the enzyme, N-acetylgalactosamine 6-sulfatase, which is needed to break down keratan sulfate, is absent or present in only very small quantities. An excessive amount of keratan sulfate results in the clinical symptoms of Morquio type A/MPS IV A.

There are two forms of Morquio MPS IV: Type A and Type B. Type A is the most 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 together is estimated to be one in 200,000 live births worldwide.

Symptoms:
Typically, symptoms begin to appear at around 18 months of age. The wide range of symptoms for Morquio MPS IV Type A is classified into the following sections:

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 at around eight years of age, with their final height measuring between three and four feet.

Curvature of the spinal column creates deformity of the rib cage and chest. This chest deformation results in restricted breathing as well as serious chest and lung infections. Other bone abnormalities are common, such as dislocated hips or shoulders, knock-knees, weak wrists, loose joints, scoliosis as well as an unstable neck, which can lead to nerve damage or paralysis.

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 A/MPS IV A.

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

Organ damage:
Leaky or blocked heart valves, heart murmurs, hernias as well as an enlarged liver and spleen are symptoms associated with this disorder.

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

Life Expectancy:
Life expectancy for individuals with mild Morquio type A/MPS IV A is 60 years of age. Life expectancy for individuals with severe Morquio type A/MPS IV A is 30 years of age or younger.

Diagnosis and Testing:
A urine test can provide a diagnosis of Morquio type A/MPS IV A. It measures increased levels mucopolysaccharides, the type of sugar chain in the lysosome that accumulates 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 N-acetylgalactosamine 6-sulfatase. Prenatal screening is available to examine N-acetylgalactosamine 6-sulfatase activity in the fetus. Genetic testing is also available in combination with these diagnostic tests to look for the mutation that causes Morquio type A/MPS IV A.

Treatment:
There is no cure for Morquio type A/MPS IV A. In most cases, treatment is limited to reducing or controlling the symptoms of this disorder by making sure that neurologists, ophthalmologists, orthopedists, cardiologists and genetic counselors are consulted routinely. 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 may also be avoided to reduce the amount of mucus production or if diarrhea is present. Exercise is highly encouraged to maintain muscle strength, as is 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 may be recommended to control the unstable neck characteristic of this disorder. Hip and/or knee replacement surgery may also be necessary. A back brace is often used to slow the progression of scoliosis and delay the necessity of back surgery.

Bone marrow transplants have been utilized as a possible treatment option but have not proven effective at reducing the progression of the disorder or at halting its course. There is hope that enzyme replacement therapy will produce a cure in the coming years.

Patient Groups:
International Morquio Organization
8164 W. Circulo De Los Morteros
Tucson, AZ 85743
www.morquio.com
tel: (520) 744-2531
fax: (520) 744-2535
Mary Smith, President
mbs85705@yahoo.com

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