Morquio Syndrome is a rare genetic disorder affecting various parts of the body. This article describes its symptoms, providing clarity on how it manifests and its impact.
Defining Morquio Syndrome
Morquio Syndrome, also known as Mucopolysaccharidosis Type IVA (MPS IVA) or Type IVB (MPS IVB), is a lysosomal storage disorder. It arises from a deficiency in specific enzymes that break down complex sugar molecules called glycosaminoglycans (GAGs), particularly keratan sulfate. In Morquio A, the deficient enzyme is N-acetylgalactosamine-6-sulfatase (GALNS), while in Morquio B, it is beta-galactosidase (GLB1). This enzyme deficiency leads to an accumulation of keratan sulfate within cells, primarily affecting connective tissues. Morquio Syndrome is an inherited condition, passed down through an autosomal recessive pattern, meaning an individual must inherit a copy of the altered gene from each parent.
Key Physical Symptoms
Individuals with Morquio Syndrome often exhibit physical characteristics affecting their skeletal structure and connective tissues. A prominent feature is short stature, with a significantly short torso and stunted neck, alongside distinctive facial features like mildly coarse features, a broad mouth, a short nose, and widely spaced teeth. Common skeletal deformities include knock-knees, bowed legs, a pigeon chest (pectus carinatum), and flared ribs, contributing to a barrel-shaped chest. Joint hyperlaxity, or excessive flexibility, is frequently observed, particularly in the wrists and smaller joints. Spinal abnormalities are also a significant concern, encompassing kyphosis (a forward curvature), scoliosis (a sideways curvature), flattened vertebrae (platyspondyl), and atlantoaxial instability, which affects neck stability.
Impact on Other Body Systems
Beyond the skeletal system, Morquio Syndrome can affect other body systems. Ocular symptoms may include corneal clouding, which can lead to visual disturbances and light sensitivity. Hearing loss is common, which can be conductive, sensorineural, or a combination, often accompanied by frequent ear infections. Respiratory issues are frequently encountered due to abnormalities in the trachea and bronchi, leading to airway narrowing, sleep apnea, and increased susceptibility to infections. The chest wall changes can also strain the heart and lungs.
Cardiac problems, such as heart valve disease, including mild mitral or aortic valvular issues, and heart murmurs, can develop over time. Dental abnormalities are noted, often presenting as widely spaced teeth, thin enamel, and a propensity for dental caries and fractures. Morquio Syndrome typically does not affect cognitive development.
Symptom Progression and Variation
Symptoms of Morquio Syndrome usually appear in early childhood, typically between ages one and three. As keratan sulfate accumulates, symptoms tend to progressively worsen. The presentation and severity of symptoms can vary significantly among individuals, even within the same type. Morquio A is generally associated with more severe symptoms than Morquio B, where symptoms tend to be milder and progress more slowly. Early diagnosis plays a role in symptom management, allowing for timely interventions.