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Disease Profile

Mucopolysaccharidosis type IV

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-5 / 10 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

MPS4; MPSIV; Mucopolysaccharidosis type 4;


Congenital and Genetic Diseases; Eye diseases; Musculoskeletal Diseases


Mucopolysaccharidosis type IV (MPS IV), also known as Morquio syndrome, is a rare metabolic condition in which the body is unable to break down long chains of sugar molecules called glycosaminoglycans. As a result, toxic levels of these sugars accumulate in cell structures called lysosomes, leading to the various signs and symptoms associated with the condition. Affected people generally develop features of MPS IV between the ages of 1 and 3. These signs and symptoms may include abnormalities of the skeleton, eyes, heart and respiratory system. There are two forms of MPS IV:

Both forms are inherited in an autosomal recessive manner. Treatment is based on the signs and symptoms present in each person.[1][2][3]


People affected by mucopolysaccharidosis type IV (MPS IV) often develop signs and symptoms of the condition in early childhood. The condition is considered progressive; however, the rate at which symptoms worsen varies significantly among affected people. All people affected by MPS IV develop skeletal problems such as scoliosis, knock-knees, short stature, pectus carinatum and variety of other abnormalities of the ribs, chest, spine, hips, and wrists.[1][4] Another common feature of MPS IV is an underdeveloped odontoid process (a peg-like bone in the neck that helps stabilize the cervical vertebrae). This can misalign, compress and damage the spinal cord, leading to paralysis or even death.[1]

Other features of the condition include:[1][5]

  • Coarse facial features
  • Hypermobile joints
  • Corneal clouding and vision loss
  • Heart valve abnormalities
  • Respiratory complications, including airway obstruction, sleep apnea and restrictive lung disease
  • Widely-spaced, discolored teeth with thin enamel
  • Mild to moderate hearing loss
  • Mild hepatomegaly

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormality of epiphysis morphology
Abnormal shape of end part of bone
Abnormality of the metaphysis
Abnormality of the wide portion of a long bone
Abnormality of the ribs
Rib abnormalities
Corneal opacity
Delayed skeletal maturation
Delayed bone maturation
Delayed skeletal development

[ more ]

Gait disturbance
Abnormal gait
Abnormal walk
Impaired gait

[ more ]

Genu valgum
Knock knees
Hearing impairment
Hearing defect

[ more ]

Joint hyperflexibility
Joints move beyond expected range of motion
Pectus carinatum
Pigeon chest
Reduced bone mineral density
Low solidness and mass of the bones
Short neck
Decreased length of neck
Short stature
Decreased body height
Small stature

[ more ]

Short thorax
Shorter than typical length between neck and abdomen
30%-79% of people have these symptoms
Abnormal heart valve morphology
Anteverted nares
Nasal tip, upturned
Upturned nasal tip
Upturned nose
Upturned nostrils

[ more ]

Carious teeth
Dental cavities
Tooth cavities
Tooth decay

[ more ]

Coarse facial features
Coarse facial appearance
Coxa valga
Grayish enamel
Gray colored tooth enamel
Greyish enamel

[ more ]

Prominent swayback
Joint dislocation
Joint dislocations
Recurrent joint dislocations

[ more ]

Hunched back
Round back

[ more ]

Flattened vertebrae
Spinal canal stenosis
Narrow spinal canal
Wide mouth
Broad mouth
Large mouth

[ more ]

5%-29% of people have these symptoms
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment

[ more ]

Increased size of skull
Large head
Large head circumference

[ more ]



There are two forms of mucopolysaccharidosis type IV (MPS IV): type A and type B. Type A is caused by changes (mutations) in the GALNS gene and type B is caused by mutations in the GLB1 gene. Both of these genes encode enzymes that help the body breakdown large sugar molecules called glycosaminoglycans (GAGs). If mutations reduce or eliminate the amount of these enzymes functioning in the body, GAGs accumulate in specialized cell structures called lysosomes (compartments in the cell that break down and recycle different types of molecules). This buildup of GAGs is toxic to various tissues in the body and leads to the signs and symptoms associated with the condition.[6][2]


A diagnosis of mucopolysaccharidosis type IV is often suspected based on the presence of characteristic signs and symptoms. Additional testing can then be ordered to confirm the diagnosis, determine the severity of the condition and rule out other conditions that can be associated with similar features. These tests may include:[1][3]

  • X-rays
  • Specialized urine and blood tests
  • Eye exam
  • Skin fibroblast culture
  • Genetic testing to identify mutations in the GALNS or GLB1 genes


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

    • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
    • Genetics Home Reference (GHR) contains information on Mucopolysaccharidosis type IV. This website is maintained by the National Library of Medicine.
    • The National Institute of Neurological Disorders and Stroke (NINDS) (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.
    • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
      • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.


        1. Debra S Regier, MD, PhD, Matthew Oetgen, MD, and Pranoot Tanpaiboon, MD. Mucopolysaccharidosis Type IVA. GeneReviews. March 2016; https://www.ncbi.nlm.nih.gov/books/NBK148668.
        2. Kazuki Sawamoto, PhD, MS. Morquio Syndrome (Mucopolysaccharidosis Type IV). Medscape Reference. July 2017; https://emedicine.medscape.com/article/947254-overview.
        3. Mucopolysaccharidosis IV. National Organization for Rare Disorders. 2016; https://rarediseases.org/rare-diseases/morquio-syndrome/.
        4. Di Cesare A, Di Cagno A, Moffa S, Teresa P, Luca I, Giombini A. A description of skeletal manifestation in adult case of morquio syndrome: radiographic and MRI appearance. Case Rep Med. 2012; 2012:324596.
        5. Robert Wynn, MD, MRCP, FRCPath. Mucopolysaccharidoses: Clinical features and diagnosis. UpToDate. June 2017; Accessed 7/24/2017.
        6. Mucopolysaccharidosis type IV. Genetics Home Reference. July 2010; https://ghr.nlm.nih.gov/condition/mucopolysaccharidosis-type-iv.

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