Morquio syndrome: Abnormalities of the face and skeleton

Morquio syndrome is a metabolic disease in which the body cannot break down long chains of sugar molecules because a substance is missing or insufficiently present. These chains of molecules are known as “glycosaminoglycans” (formerly mucopolysaccharides). The syndrome belongs to a group of mucopolysaccharidoses (MPS). The condition is characterized by severe skeletal abnormalities, a flattening of vertebrae with spinal deformities and dwarfism. A medication is available to treat the condition. Nevertheless, numerous (serious) complications are possible and the life expectancy of patients with the disease is shortened. L. Morquio, a Uruguayan pediatrician (1867–1935), first described the disease in 1929.

  • Synonyms Morquio syndrome
  • Epidemiology condition
  • Types and causes of metabolic disease
  • Symptoms: Abnormalities of the face and skeleton
  • Diagnosis and examinations
  • Therapy
  • Prognosis of the condition is variable
  • Complications disease

Synonyms Morquio syndrome

The Morquio syndrome is also known by these synonyms:

  • beta galactosidase deficiency
  • galactosamine-6-sulfatase deficiency
  • MPS IV
  • mucopolysaccharidosis IV
  • osteochondrodystrophy
  • Morquio-Brailsford disease

Epidemiology condition

Morquio syndrome is a rare disease that affects men and women equally. The prevalence varies between 1/40,000 to 1/300,000 births. In the Netherlands, approximately one child is born with the disease every year. Most patients (95%) are affected by type A.

Types and causes of metabolic disease

Typing

Morquio syndrome exists in type A and type B. Patients with type A do not have the substance (enzyme) galactosamine-6-sulfatase due to mutations (changes) in the GALNS gene. Patients with type B do not produce enough beta-galactosidase (also an enzyme) due to mutations in the GLB1 gene. The body needs these enzymes to break down long chains of sugar molecules (keratan sulphate sugar chains). In both types, this causes abnormally large amounts of glycosaminoglycans to build up in the body, potentially causing damage to the organs.

Hereditary disorder

Morquio syndrome is a hereditary condition that is inherited in an autosomal recessive manner. The syndrome manifests itself when the child has inherited two copies of abnormal genes from the parents.

Symptoms: Abnormalities of the face and skeleton

The symptoms of the most severe form (type A) usually appear between the ages of one and three years and are rapidly progressive. In the other form (type B), progression is slower and symptoms become visible around adolescence. The face and skeleton are particularly affected, but the severity varies per patient.

Sight

The patient has typical facial abnormalities with a large head (macrocephaly), coarse facial features, a wide mouth, prominent cheekbones, a cloudy cornea, an unusually small nose and widely spaced teeth.

Skeleton

Furthermore, abnormal development of the bones takes place. For example, this causes an abnormal backward curvature of the spine (kyphosis), a sideways curvature of the spine (scoliosis) or a combination of these (kyphoscoliosis). Other skeletal abnormalities include a chicken breast (pectus carinatum) (thoracic abnormality), short stature (dwarfism) with a particularly short trunk, bow legs (genua valga) and flat feet. Furthermore, hypermobility (pain in joints and muscles and fatigue) is also characteristic of Morquio syndrome. This means that the elbows, wrists, hips, knees and other large joints are abnormally flexible, making them unstable. Hip pain and stiffness are type B symptoms that tend to come on slowly and are usually not apparent until adolescence.

Other symptoms

Other symptoms include high-frequency hearing loss, weakness in the legs and/or other abnormalities.

Diagnosis and examinations

Physical examination

The doctor conducts a physical examination during which he identifies the following signs of the disease:

  • an abnormal curvature of the spine
  • a short stature (especially a short torso)
  • a cloudy cornea
  • an enlarged liver (hepatomegaly)
  • a loss of nerve function below the neck
  • heart murmur
  • hernia in the groin

Diagnostic research

A urinalysis reveals an additional amount of mucopolysaccharides. However, the specific form of MPS cannot be determined with a urine test. This requires a genetic test. The doctor also performs a complete blood test, an echocardiography (examination of the heart using sound waves), a hearing examination, a slit lamp eye examination, a skin fibroblast culture and an X-ray of the long bones, ribs and spine. Patients with Morquio syndrome also receive an MRI examination of the bottom of the skull and the top of the neck because sometimes the upper vertebrae in these patients are underdeveloped.

Differential diagnosis

Other conditions also resemble the clinical picture of Morquio syndrome and are therefore useful as a differential diagnosis:

  • GM1 gangliosidosis
  • spondyleopiphyseal dysplasia (SED)
  • Legg-Calve-Perthes disease (hip disorder in children)

Therapy

The drug Elosulfa alfa (Vimizim) is available for treating Morquio syndrome, which was approved in America in 2014. The patient receives this weekly through a vein (IV, intravenous). The doctor also performs a surgical procedure (spinal fusion) to prevent permanent spinal cord injury (spinal cord injury: damage to the spinal cord) in patients whose neck bones are underdeveloped. Other symptoms receive supportive and symptomatic treatment. For example, the patient is given a hearing aid if he or she has hearing problems.

Prognosis of the condition is variable

Cognitive function (the ability to think clearly) is usually normal in patients with Morquio syndrome. The life expectancy of patients with MPS IV depends on the severity of symptoms. Severely affected patients survive into late childhood or adolescence. When the patient has a milder form of the condition, he usually lives into adulthood, although life expectancy is shortened. Spinal cord compression and airway obstruction are the leading causes of death in patients with Morquio syndrome.

Complications disease

The bone problems sometimes lead to significant complications. For example, the bones at the top of the neck sometimes slip and damage the spinal cord, causing paralysis. The doctor solves these problems through surgery. Occasionally serious heart problems arise that sometimes even lead to death. The following complications occur with Morquio syndrome:

  • breathing problems: The deformation of the chest puts pressure on the heart and lungs, eventually causing respiratory failure.
  • heart failure (poor pumping of blood by the heart)
  • walking problems due to an abnormal curvature of the spine and other bone problems
  • vision problems
  • spinal cord damage and possible paralysis