SNP Shot: Genomic Insights

Morquio syndrome, or mucopolysaccharidosis type IV (MPS IV), is a disease that worsens over time and primarily affects the bones. The speed at which symptoms progress differs from person to person.

Symptoms of MPS IV typically start to appear in early childhood. Individuals affected by MPS IV develop a range of skeletal problems, such as short height, knock-knees, and deformities of the ribs, chest, spine, hips, and wrists. Individuals with MPS IV often have very flexible joints (hypermobility), but some joints may also have limited movement. A defining characteristic is the incomplete development (hypoplasia) of the odontoid process, a peg-shaped bone in the neck. This bone helps stabilize the cervical vertebrae (spinal bones in the neck). If the odontoid process is underdeveloped, it can lead to misalignment of the cervical vertebrae, potentially compressing and harming the spinal cord, which could result in paralysis or death.

Individuals with MPS IV commonly develop clouding of the cornea (the clear front part of the eye), leading to vision problems. Some individuals may experience repeated ear infections and hearing impairment. In some cases, the airway may narrow, causing frequent upper respiratory infections and brief interruptions in breathing during sleep (sleep apnea). Other frequent signs include slightly "coarse" facial features, thin enamel on the teeth, numerous dental cavities, heart valve issues, a somewhat enlarged liver (hepatomegaly), and a soft bulge near the belly button (umbilical hernia) or in the lower abdomen (inguinal hernia). Unlike some other forms of mucopolysaccharidosis, MPS IV does not affect cognitive abilities.

The lifespan of individuals with MPS IV varies based on the severity of the condition. Those with severe cases may only live into late childhood or their teenage years. Individuals with milder forms typically live into adulthood, although their lifespan might be shorter. Spinal cord compression and blocked airways are primary causes of death in individuals with MPS IV.

Inheritance:

MPS IV is inherited through an autosomal recessive pattern. This means that both copies of the responsible gene in each cell must have a mutation for the condition to develop. Individuals with an autosomal recessive condition inherit one copy of the mutated gene from each parent, who are usually carriers without showing symptoms themselves.