Morquio A - MPS 4

Medicine Community & Research
Aug 2, 2024
3 min read

By: Nysa Vinod & Aaria Lankireddy

From Unsplash

What is Morquio A?

Morquio A is a rare genetic condition found in cells of the human body. This genetic condition is passed down from your parents and/or ancestors. Morquio A is related to 2 parts of your cells and DNA. GAGs and GALNs. GAGs are like trash that builds up in our cells. GALNs break down the GAGs. In our DNA, we have two sets of every chromosome. In a person with Morquio A, both sets of chromosomes don’t have the correct way to make the GALNs. This causes the GAGs to build up.

This is what Morquio A is. “This syndrome is a progressive disease” (The Children’s Hospital of Philadelphia, 2024). Morquio A’s Scientific name is mucopolysaccharidosis. Morquio A is also called MPS 4. Mucopolysaccharides are chains of sugar molecules used to build up connective tissues in the body. “Muco” refers to the thick jelly-like consistency of the molecules. “Poly” means many. “Saccharide” is a general term for a sugar molecule. Morquio syndrome was named after Luis Morquio, a pediatrician who published his first case that he detected in a Swedish family in 1929. Morquio syndrome occurs once in every 200,000 births.

Morquio syndrome is characterized by a unique skeletal dysplasia, which results in a shortened height, prominent forehead, abnormal face with a large mandible, short neck, cervical spine instability, spinal deformity, tracheal deviation, and obstruction, and flaring of the rib cage, MPS 4 can present with hip pain and stiffness in adolescence years. Individuals with MPS 4 Type A have normal intelligence.

GAGs & GALNs

GAG's scientific name is glycosaminoglycans.GALNs scientific name is galactosamine . Gags are like trash and GALNs are like vacuum cleaners that break down the GAGs.

The purple circles are the GAGs and the blue circles inside are the GALNs. A defect in the GALNS gene causes type A. “People with type A do not have an enzyme called N-acetylgalactosamine-6-sulfatase. The body needs these enzymes to break down long strands of sugar molecules called keratan sulfate. In both types, abnormally large amounts of glycosaminoglycans build up in the body. This can damage bodily organs.” (Icahn School of Medicine at Mount Sinai, 2024).

Physical Symptoms

Symptoms appear during the ages of 1-3 years. Symptoms include
Knock Knees( Both knees point inward)
Bones look out of place
Curved spine
Unusual Chest Growth
Ribs shaped like a bell that is flared out at the bottom
Cloudy cornea
Course face features and large head
Liver enlarged
Heart murmur

“There are over 270 mutations of the GALNS gene, which may be why people with Morquio A experience varying symptoms and disease severity.” (Biomarin Pharamaceutical, 2024).

Detection

If you suspect you or someone you know has this condition, visit a clinic. The doctors may have you take a urine test. This test lets doctors see if you have an irregular or regular amount of GAGs in your cells. The regular amount is 50-70 mg/ml. Other times doctors will have you do molecular testing, echocardiogram, hearing tests, and X-ray of the upper neck and lower skull. This determines the same thing but using your blood or saliva.

Genetic Map

Treatment Options

There is 1 treatment in their current ongoing trial enzyme adjusting treatment period. Currently it is not an approved Enzyme Replacement Therapy for MPS 4, although it is a promising research. At present, there is one treatment that is approved, this treatment is called VIMIZIM. VIMIZIM (elosulfase alfa) is an enzyme-adjusting treatment. This is an enzyme replacement therapy to make up for the missing enzyme that causes Morquio A. VIMIZIM helps to replace the deficient GALNS to help restore some cell function.

VIMIZIM is given as an intravenous (IV) infusion directly into a vein once a week for 4 hours. A doctor may reduce the time necessary if a patient does well with VIMIZIM. Some side effects of VIMIZIM are vomiting, fever, headache, fatigue, and abdominal pain.

As a child with MPS 4 grows older, the knees gradually become more “knocked” (genu valgum), facing together. It is sometimes possible for the legs to be straightened by an operation when the child has stopped growing. Morquio syndrome patients will need to see several specialists throughout childhood and adolescence.

Effects of VIMIZIM

Some common and serious side effects includes:

Fever, vomiting, headache, nausea, abdominal pain, chills, and exhaustion
Breathing difficulties, hives or rashes, itching, fast heartbeat, tightness in the throat, dizziness, and swelling in the face or tongue
Hypersensitivity reactions, life-threatening allergic reactions, spinal cord compression, coughing, and shortness of breath