Mucopolysaccharidosis IV [Morquio’s Syndrome]

Mucopolysaccharidoses are the group of genetic disorders, characterized by the excretion of mucopolysaccharide in the urine.



The mucopolysaccharidoses constitute the largest group of lysosomal storage diseases.



The intracellular degradation of micromolecular compounds by lysosomal enzymes is abnormal in this group of diseases, leading to intracellular accumulation of semi degraded compounds.



Morquio’s syndrome is the most common type of mucopolysaccharidoses.



There are two types of Morquio’s syndrome – A and B subtype.

Morquio’s syndrome type A –


The deficient enzyme is N-acetylgalactosamine-6-sulfate sulfates.


Gene is located on chromosome 16.


Accumulation of keratin sulfate and chondroitin-6-sulfate is present.



Morquio’s syndrome type B –


The deficient enzyme is beta-galactosidase.

Morquio’s syndrome type A –


Normal at birth, however, exhibit growth failure as infants.


Intelligence is normal


The average age at diagnosis is 48months.


Thoracolumbar kyphosis, first deformity noted by the parents.


Genu valgum.


Dwarfism – Short trunk.


The child stands with knees and hips flexed in a crouched position.


Eyes are wide-set, the nasal bridge is depressed and maxilla is prominent.


The abdomen may protrude, but hepatosplenomegaly is not present.


Epiphyses of the knees, elbow, shoulders, wrists, and ankles appear enlarged.


Generalized joint laxity is present.


Ankle valgus and flatfeet are present.


Waddling gait with short hands and feet are present.


Corneal opacities develop.


All patients have hearing loss by the end of the first decade.


Silent cardiac abnormalities are mitral and aortic valve thickening and stenosis.


Pectus carinatum is present.



Morquio’s syndrome type B –


Presents at a later age


Normal intelligence and no neurologic abnormalities


Dysostosis multiplex, dwarfism, odontoid anomalies, and cloudy corneas.

Morquio’s syndrome type A –


Vertebral bodies in the thoracic and lumbar spine are ovoid in infancy but with time they become flattened – Platyspondyly.


A central tongue or anterior beak becomes obvious in the lower thoracic and upper lumbar vertebrae.


Disks are narrower than normal.


Kyphosis is common.


Hypoplasia or absence of an odontoid process is a characteristic feature of Morquio’s syndrome.


Epiphyses of long bones ossify irregularly, resulting in broad and flat epiphyses.


Ossification of femoral heads is delayed, and femoral necks are widened. Coxa vara or valga may occur.


The acetabulum is dysplastic


The pelvis becomes narrow with growth, resulting in a wine glass shape to the inner pelvic contour and iliac wings are flared laterally.


A delay in the ossification of the lateral proximal tibial epiphysis is common.


The metaphyses are widened, but the diaphyses are relatively normal.


The carpals and tarsals are irregular, and their ossification is delayed. There is a central constriction of the diaphyses of the metacarpals, phalanges, and metatarsals. The bases of the second through fifth metacarpals are pointy.

The diagnosis of Morquio’s syndrome is made with a positive test for urinary keratan sulfate.


Urinary keratan sulfate concentrations peak between the ages of 1 and 5 years.


Blood keratin sulfate levels are also elevated in patients with Morquio’s syndrome


Prenatal diagnosis of Morquio’s syndrome is possible. Cells present in the amniotic fluid are assayed for the presence of N-acetylgalactosamine-6-sulfate sulfatase. An absence of enzyme activity is predictive of the diagnosis of Morquio’s syndrome type A.

Odontoid hypoplasia – Posterior spinal fusion.


Genu valgum – Realignment osteotomy.