What is MPS IV A?

Mucopolysaccharidosis IV A (MPS IV A), also known as Morquio A syndrome, is a rare genetic disorder that affects the body’s ability to break down and recycle certain complex sugars called glycosaminoglycans (GAGs). This results in the accumulation of GAGs in the body’s tissues and organs, leading to a range of physical and developmental problems.

MPS IV A is caused by mutations in the GALNS gene, which provides instructions for making an enzyme called N-acetylgalactosamine-6-sulfatase. This enzyme is necessary for breaking down and recycling GAGs, specifically keratan sulfate and chondroitin-6-sulfate. In individuals with MPS IV A, the GALNS gene mutation results in a deficiency of this enzyme, leading to the accumulation of GAGs in the body.

The accumulation of GAGs in the body can cause a range of physical symptoms, including skeletal abnormalities, joint pain and stiffness, short stature, and a distinct facial appearance. The skeletal abnormalities can include a flattened chest, abnormal curvature of the spine, and deformities of the bones in the arms and legs. Joint pain and stiffness can make it difficult for affected individuals to move and perform everyday activities. The distinct facial appearance can include a large head, bulging forehead, widely spaced teeth, and a flattened bridge of the nose.

In addition to these physical symptoms, MPS IV A can also affect the development and function of other organ systems. The accumulation of GAGs in the heart can lead to heart valve problems, while the accumulation in the lungs can cause breathing difficulties. The accumulation in the eyes can cause vision problems, while the accumulation in the ears can cause hearing loss. The accumulation in the liver and spleen can cause organ enlargement and damage.

MPS IV A is inherited in an autosomal recessive pattern, which means that affected individuals inherit two copies of the mutated GALNS gene, one from each parent. Carriers of the mutated gene do not typically show symptoms, but have a 50% chance of passing the mutation on to their children.

There is currently no cure for MPS IV A, and treatment focuses on managing the symptoms and complications of the disorder. Enzyme replacement therapy (ERT) is a treatment option that involves the infusion of the missing enzyme into the bloodstream to help break down and remove GAGs from the body. However, ERT is not effective in treating the skeletal abnormalities associated with MPS IV A. Physical therapy, surgery, and other supportive treatments may also be used to manage symptoms.

The prognosis for individuals with MPS IV A can vary depending on the severity of symptoms and complications. Some individuals may have a relatively mild form of the disorder, while others may experience significant developmental delays and life-threatening complications. Regular medical follow-up and close monitoring can help ensure that affected individuals receive appropriate care and treatment.

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