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# Morquio syndrome (mucopolysaccharidosis type IV)

Morquio syndrome is a mucopolysaccharidosis that mainly hits the skeleton: short stature, knock knees and a weak neck joint, with normal intelligence.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Axis (C2)](https://durgical.com/en/anatomy/axis/)
- [Atlas–axis joints](https://durgical.com/en/anatomy/median-and-lateral-atlanto-axial-joints/)
- [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/)
- [Cornea](https://durgical.com/en/anatomy/cornea/)
- [Atlas (C1)](https://durgical.com/en/anatomy/atlas/)
- [Transverse ligament of the atlas](https://durgical.com/en/anatomy/transverse-ligament-of-atlas/)
- [Sternum](https://durgical.com/en/anatomy/sternum/)
- [Ribs (back part)](https://durgical.com/en/anatomy/ribs/)
- [Femur](https://durgical.com/en/anatomy/femur/)
- [Tibia](https://durgical.com/en/anatomy/tibia/)
- [Aortic right coronary cusp](https://durgical.com/en/anatomy/right-coronary-leaflet/)
- [Trachea](https://durgical.com/en/anatomy/trachea/)

## In biochemistry

- [Lysosomal storage diseases](https://durgical.com/en/biochemistry/topics/lysosomal-storage-diseases/)

## What it is

An autosomal recessive lysosomal disease in which keratan sulfate (and, in type A, chondroitin 6-sulfate) cannot be broken down and builds up mainly in cartilage, bone and [cornea](https://durgical.com/en/anatomy/cornea/).

## Who gets it

Estimated at 1 in 200 000 to 300 000 people. No Colombian frequency is given in the sources consulted.

## Causes

- MPS IVA: GALNS variants (N-acetylgalactosamine 6-sulfatase)
- MPS IVB: GLB1 variants (β-galactosidase, the same gene as GM1 gangliosidosis)

## Risk factors

- Both parents carriers
- Consanguinity

## Pathophysiology

GALNS removes a sulfate from keratan sulfate and chondroitin 6-sulfate, and β-galactosidase then removes galactose from keratan sulfate. When either step fails, these GAGs fill the lysosomes of chondrocytes, disturbing growth plates and producing a skeletal dysplasia. Keratan sulfate is abundant in cartilage and cornea, which explains the bone deformities and corneal clouding; the brain is spared.

## Classification

- MPS IVA (GALNS): most cases
- MPS IVB (GLB1): clinically very similar
- Severe and attenuated forms on a continuum

## Symptoms and signs

- Short stature with short trunk
- Knock knees (genu valgum) and loose, hypermobile joints
- Pectus carinatum and rib, spine, hip and wrist deformities
- Odontoid hypoplasia with neck instability
- Corneal clouding
- Thin tooth enamel and many cavities
- Hearing loss, narrow airway and sleep apnoea
- Normal intelligence

## Red flags

- Neck pain, weakness, clumsy gait or bladder changes (cervical cord compression)
- Snoring with breathing pauses or noisy breathing
- Breathlessness or signs of valve disease
- Anaesthesia or intubation planned (difficult airway, neck instability)

## Diagnosis

**Clinical**
A child of normal intelligence with short-trunk dwarfism, knock knees, pectus carinatum, joint laxity and cloudy corneas.

**Tests**
Raised urine keratan sulfate (may be normal in older patients); low GALNS or β-galactosidase activity in leukocytes or fibroblasts; GALNS or GLB1 gene testing; audiometry and sleep study.

**Imaging**
Skeletal survey with flattened vertebrae (platyspondyly) and dysostosis; flexion–extension cervical X-rays and MRI for odontoid hypoplasia and cord compression; echocardiogram for valves.

## Treatment

**Medical**
Intravenous enzyme replacement with recombinant GALNS for MPS IVA improves endurance and urinary keratan sulfate; it does not reverse established bone changes.

**Surgical**
Upper cervical (occipitocervical) fusion for instability or cord compression; osteotomies for knock knees; hip and [spine](https://durgical.com/en/anatomy/region/spine/) surgery as needed.

**Procedure**
Non-invasive ventilation for sleep apnoea; anaesthesia planned by an experienced team with neck protection.

**Follow-up**
Regular neurological, cervical spine, respiratory, cardiac, eye and hearing follow-up.

## Complications

- Cervical cord compression with paralysis
- Airway obstruction and respiratory failure
- Valve disease
- Vision and hearing loss
- Early joint degeneration

## Prognosis

Severe forms may survive only to late childhood or adolescence; milder forms reach adulthood. [Spinal cord](https://durgical.com/en/anatomy/spinal-cord/) compression and airway obstruction are the main causes of death.

## Prevention

- Genetic counselling and carrier testing in families
- Early cervical screening to prevent cord injury

## Test yourself

Think of the answer, then tap the question to see it.

## Which GAG accumulates in Morquio syndrome?

Keratan sulfate (with chondroitin 6-sulfate in type A), abundant in cartilage and cornea.

## Which spinal finding makes Morquio syndrome dangerous?

Odontoid hypoplasia: the C1–C2 joint becomes unstable and can compress the cervical spinal cord, causing paralysis.

## How does Morquio syndrome differ from Hurler and Sanfilippo syndromes in the brain?

Intelligence is normal in Morquio syndrome, because keratan sulfate storage spares the brain.

## Which enzymes are missing in MPS IVA and MPS IVB?

IVA: N-acetylgalactosamine 6-sulfatase (GALNS); IVB: β-galactosidase (GLB1).

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## Related conditions

- [Sanfilippo syndrome (mucopolysaccharidosis type III)](https://durgical.com/en/conditions/sanfilippo-syndrome/)
- [Hurler syndrome (mucopolysaccharidosis type I)](https://durgical.com/en/conditions/hurler-syndrome/)
- [GM1 gangliosidosis](https://durgical.com/en/conditions/gm1-gangliosidosis/)
- [Obstructive sleep apnoea](https://durgical.com/en/conditions/obstructive-sleep-apnoea/)
- [Degenerative cervical myelopathy](https://durgical.com/en/conditions/degenerative-cervical-myelopathy/)
- [Spinal cord injury](https://durgical.com/en/conditions/spinal-cord-injury/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Mucopolysaccharidosis type IV: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/mucopolysaccharidosis-type-iv/) (MedlinePlus, US National Library of Medicine, 2026); [GALNS gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/galns/) (MedlinePlus, US National Library of Medicine, 2026); [GLB1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/glb1/) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Source: https://durgical.com/en/conditions/morquio-syndrome/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/morquio-syndrome/