Morquio Syndrome is another name for mucopolysaccharidosis IV (MPS IV); it was first described by Luis Morquio in 1919 (4). The frequency of Morquio syndrome is 1 in 640,000 births (7).
A mutation is the GALNS gene, which encodes for N-acetyl galactosamine-6-sulfatase, causes Morquio, type A (4). Type B is caused by mutations of the GLB1 gene, which encodes for β-galactosidase (4). Both enzymes, however, are responsible for keratan sulfate degradation. In type A, the activity of the sulfatase was found to be less than 1% (6). Due to the enzymes’ ineffectiveness, mucopolysaccharides aggregate within intracellular lysosomes. Mucopolysaccharides are long, unbranched chains of repeating saccharide, or sugar, units. They are important components of the body’s connective tissues and are often times covalently linked to proteins. In Morquio Syndrome, the lysosomal enzymes that are responsible for breaking down mucopolysaccharides are ineffective. As a result, the long sugar molecules begin to collect in the body’s cells and connective tissues. The accumulation ultimately causes cellular damage that manifests as skeletal malformations.
Face and Skull
- mildly coarse facial features
- accentuated lower portion of the face
- broad mouth
- short anteverted nose
- corneas of the eyes become cloudy
- widely spaced teeth
- hypoplasia of tooth enamel
Trunk, Chest and Spine:
- barrel shaped chest
- flaring lower rib cage
- prominent sternum
- stunted neck and trunk
- considerably short spine marked platyspondyly
- abnormal posture
Arms and Legs:
- severe flexion deformities of the limbs
- ligamentous laxity, especially at the wrists and small joints
- joint restriction prominent at the larger joints, most notably at the hips
- awkward gait
- flat feet
- prominent buttocks
- short and stubby hands
What Are the X-Ray Characteristics?
The major radiographic features of Morquio syndrome include marked platyspondyly in the thoracic and lumbar spine. The shape of the vertebrae change from ovoid, to ovoid with anterior projection, to flat.
Odontoid hypoplasia with atlantoaxial instability is typical. With progression of the disease, acute thoracolumbar kyphosis is possible; the first indication of spinal cord compression is at the level of C1/C2.The skull is mildly dolichocephalic with underdevelopment of mastoid cells and flat or concave mandibular condyles. A flaring lower rib cage with pectus carinatum is typical of the thorax.
A premature fusion of the ossification centers of the sternum usually occurs. The long bones are short and curved, with irregular tabulation. Metaphyses are irregularly wide. Ossification centers tend to develop slowly. Coxa valga is characteristic, along with an abnormal femoral neck and flattening of the femoral head.
Genu Valgus and a medial spur of tibial metaphysis are often times seen. The bases of the second through fifth metacarpals are conically shaped. The feet have irregular contour with delayed ossification of the tarsal bones. There is central constriction and general shortness of the metacarpals and phalanges.
Morquio Syndrome is typically not recognized at birth. Onset does not occur until the second to fourth year of life. The most frequently recognized symptoms include gait disturbance and growth deficiency.
Diagnostic procedures include flexion-hyperextension radiographs of the cervical spine and/or MRI of the cervical or thoracolumbar spine.
To confirm the diagnosis, two-dimension electrophoresis or thin-layer chromatography of isolated urinary glycosaminoglycans is employed.
Heterozygote detection is possible.
Prenatal recognition can be done using amniotic fluid cells and chorionic villi.
Pectus carinatum and knock-knee deformity (genu valgus) begin at approximately 3 years of age, and progressively worsen as growth continues. Ligamentous laxity plays a part in the development of knock-knee. In severe cases, the knock-knee may interfere with ambulation. Around age 7 or 8, a patient typically has a lower limb osteotomy to correct the deformity. Typically, the outcome is good, and the results are permanent because growth typically stops around this age. However, due to the habitual atlantoaxial instability, neurological integrity may be compromised, and patients have considerable difficulty in learning to walk again.
Dislocation of the hips is typically observed, especially as weight-bearing increases. The dislocation, however, is asymptomatic and usually does not impair function. Therefore, most patients abstain from surgical intervention. Yet if patients are considerably physically active, especially as adults, symptomatic osteoarthritis of the hip may develop.
Ligamentous laxity is severe, especially of the wrists and ankles. The force able to be delivered by the long flexors of the fingers and thumbs becomes considerably weak. The wrists need to be stabilized, which will help to increase the effectiveness of the muscles and to improve function. Wrist fusions have been attempted, however most attempts have failed.
Atlantoaxial instability along with myelopathy of the upper cervical spinal cord is a severe problem. Upper motor neurons begin to lose function, there is vague pain in the lower limbs, superficial paresthesias of the feet, vibratory sensation progressively worsens, mobility becomes impaired, and the ability to control the sphincters and to breathe is compromised. If left untreated, most males lose their ability to walk and may possibly die of chronic respiratory failure. The course is typically not as severe in female patients. The rate of progression of cervical myelopathy is variable, however surgical intervention is needed to halt the downward trend. Fusion of the upper cervical spine is frequently recommended. However, care must be taken when administering the anesthesia, due to the risks associated with atlantoaxial instability. Spinal fusion may be supplemented by instrumentation (metal implants) to support the bones until the fusion mass consolidates. In cases of diagnostic doubt, further information can be obtained by means of an MRI scan (with flexion-extension views and CSF flow studies). It allows accurate determination of the degree of spinal cord compression and space available for the cord.
By late teens and adulthood, the ribs are nearly horizontal and the sagittal diameter of the chest is greater than average. As a result, respiratory expansion becomes considerably impaired. Moreover, frequent upper respiratory tract infections, including otitis media, may occur due to the malformation of the rib cage. The trachea is narrow and may collapse during head flexion. Lung function tests and sleep studies are frequently used to diagnose breathing problems in skeletal dysplasias. Regular review by a pulmonologist is recommended. Prolonged breathing difficulties may warrant a tracheostomy and long-term ventilatory support.
Cardiac complications may occur, including cardiomyopathy, valvular disease, or a late onset of aortic regurgitation. Cardiac anomalies are predominately left sided. Severe cases have resulted in death before the age of 20.
Hearing loss, inguinal hernia, and hepatomegaly are all problems associated with the ear. Hearing aids and tubes are often times required.
Corneal opacity is typical once patients reach age 5; glaucoma of the eyes and pigmentary retinal degeneration may occur in older patients. Ophthalmologic examination is needed at frequent intervals.
Cutaneous abnormalities may also be present, including loose, thickened, tough, and inelastic skin, particularly of the extremities. Generalized telangiectasia of the face and limbs has also been reported.
Appropriate dental care is required due to the hypoplasia of tooth enamel. Teeth often brown and discolor easily. The permanent posterior teeth have pointed cusps; there is often times pitting of the buccal surfaces. The teeth are also widely spaced.
Intelligence and mentality is typically not impaired in Morquio type A. However, progressive mental deficiency does occur in Morquio Type B.
Although the first 18 months are characterized by relatively normal development, beyond this age, Morquio patients tend to decline, especially in proportionate growth and mobility.
Any change in walking ability, endurance, or breathing merits further assessment by a physician to rule out spinal cord compression. Specific neurological symptoms such as tingling or numbness in the arms or legs, weakness, shooting leg or arm pain, or problems controlling bladder/ bowel function should be investigated further.
Considering that eye and teeth problems are especially associated with Morquio Syndrome, ophthalmologic consultation and dental examinations are recommended for early detection and treatment.
Generally all skeletal dysplasias warrant multidisciplinary attention. Regular assessment by an orthopedist, geneticist, pediatrician, dentist, neurologist, and physical therapist will provide the most comprehensive treatment.
- Cole, D.E.C. Fukuda, S. Gordon, B.A. Rip, J.W. LeCouteur, A.N. Rupar, C.A. Tomatsu, S. Ogawa, T. Sukegawa, K. Orii, T. Heteroallelic Missense Mutations of the Galactosamine-6-Sulfate Sulfatase (GALNS) Gene is a Mild Form of Morquio Disease (MPS IVA) American Journal of Medical Genetics. 63: 558-565. 1996.
- Giugliani, R. Jackson M. Skinner S.J. Vimal C. M. Fensom A. H. Fahmy A. Sjövall. Beson, P. F. Progressive mental regression in siblings with Morquio disease Type B (mucopolysaccharidosis IV B). Clinical Genetics. 32: 313-325. 1987.
- Greaves, M.W. Inman, P. M. Cutaneous Changes in the Morquio Syndrome. Br. J. Derm. 81: 29-36. 1969.
- Jones, Kenneth L. Recognizable Patterns of Human Malformation. Philadelphia, PA: Elsevier Saunders. 2006
- Kopits, Steven E. Orthropedic Complications of Dwarfism. Clinical Orthopedics and Related Research. 144: 153-179. 1976.
- Matalon, R.; Arbogast, B.; Dorfman, A. Morquios syndrome: a deficiency of chondroitin sulfate N-acetylhexosamine sulfate sulfatase. (Abstract) Pediat. Res. 8: 436, 1974.
- Nelson, J.; Crowhurst, J.; Carey, B.; Greed, L. Incidence of the mucopolysaccharidoses in western Australia. Am. J. Med. Genet. 123A: 310-313, 2003.
- Scott, Charles I. Dwarfism. Clinical Symposium, 1988; 40(1):9-10.
- Spranger, Jurgen W. Brill, Paula W. Poznanski, Andrew. Bone Dysplasias: An Atlas of Genetic Disorder of Skeletal Development. Oxford: Oxford University Press. 2002.
- Taybi, Hooshang. Lachman, Ralph S. Radiology of Syndromes, Metabolic Disorders, and Skeletal Dysplasias. St. Louis, MO: Mosby-Year Book, Inc. 1996.
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Prenatal Genetic Counseling
If you and your partner are newly pregnant, you may be amazed at the number and variety of prenatal tests available to you. Blood tests, urine tests, monthly medical exams, screening tests, and family history tracking — each helps to assess the health of you and your baby, and to predict any potential health risks.
You may also have the option of genetic testing. These tests identify the likelihood of passing certain genetic diseases or disorders (those caused by a defect in the genes — the tiny, DNA-containing units of heredity that determine the characteristics and functioning of the entire body) to your children.
Some of the more familiar genetic disorders are:
- Down syndrome
- cystic fibrosis
- sickle cell disease
- Tay-Sachs disease (a fatal disease affecting the central nervous system)
If your history suggests that genetic testing would be helpful, you may be referred to a genetic counselor. Or, you might decide to seek out genetic counseling yourself.
But what do genetic counselors do, and how can they help your family?
What Is Genetic Counseling?
Genetic counseling is the process of:
- evaluating family history and medical records
- ordering genetic tests
- evaluating the results of this investigation
- helping parents understand and reach decisions about what to do next
Genetic tests are done by analyzing small samples of blood or body tissues. They determine whether you, your partner, or your baby carry genes for certain inherited disorders.
Genes are made up of DNA molecules, which are the building blocks of heredity. They're grouped together in specific patterns within a person's chromosomes, forming the unique "blueprint" for every physical and biological characteristic of that person.
Humans have 46 chromosomes, arranged in pairs in every living cell of our bodies. When the egg and sperm join at conception, half of each chromosomal pair is inherited from each parent. This newly formed combination of chromosomes then copies itself again and again during fetal growth and development, passing identical genetic information to each new cell in the growing fetus.
Current science suggests that every human has about 25,000 genes per cell. An error in just one gene (and in some instances, even the alteration of a single piece of DNA) can sometimes be the cause for a serious medical condition.
Some diseases, such as Huntington's disease (a degenerative nerve disease) and Marfan syndrome (a connective tissue disorder), can be inherited from just one parent. But most disorders, including cystic fibrosis, sickle cell anemia, and Tay-Sachs disease, cannot occur unless both the mother and father pass along the gene.
Other genetic conditions, such as Down syndrome, are usually not inherited. In general, they result from an error (mutation) in the cell division process during conception or fetal development. Still others, such as achondroplasia (the most common form of dwarfism), may either be inherited or the result of a genetic mutation.
Genetic tests don't yield easy-to-understand results. They can reveal the presence, absence, or malformation of genes or chromosomes. Deciphering what these complex tests mean is where a genetic counselor comes in.
About Genetic Counselors
Genetic counselors are professionals who have completed a master's program in medical genetics and counseling skills. They then pass a certification exam administered by the American Board of Genetic Counseling.
Genetic counselors can help identify and interpret the risks of an inherited disorder, explain inheritance patterns, suggest testing, and lay out possible scenarios. (They refer you to a doctor or a laboratory for the actual tests.) They will explain the meaning of the medical science involved, provide support, and address any emotional issues raised by the results of the genetic testing.
Who Should See One?
Most couples planning a pregnancy or who are expecting don't need genetic counseling. About 3% of babies are born with birth defects each year, according to the Centers for Disease Control and Prevention (CDC) — and of the malformations that do occur, the most common are also among the most treatable. Cleft palate and clubfoot, two of the more common birth defects, can be surgically repaired, as can many heart malformations.
The best time to seek genetic counseling is before becoming pregnant, when a counselor can help assess your risk factors. But even after you become pregnant, a meeting with a genetic counselor can still be helpful. A genetic counselor can help determine what testing is appropriate for your pregnancy.
Experts recommend that all pregnant women, regardless of age or circumstance, be offered genetic counseling and testing to screen for Down syndrome.
It's especially important to consider genetic counseling if any of the following risk factors apply to you:
- a standard prenatal screening test (such as the alpha fetoprotein test) yields an abnormal result
- an amniocentesis yields an unexpected result (such as a chromosomal defect in the unborn baby)
- either parent or a close relative has an inherited disease or birth defect
- either parent already has children with birth defects, intellectual disabilities, or genetic disorders
- the mother-to-be has had two or more miscarriages or babies that died in infancy
- the mother-to-be will be 35 or older when the baby is born. Chances of having a child with Down syndrome increase with the mother's age: a woman has about a 1 in 350 chance of conceiving a child with Down syndrome at age 35, a 1 in 110 chance at age 40, and a 1 in 30 chance at age 45.
- you are concerned about genetic defects that occur frequently in certain ethnic or racial groups. For example, couples of African descent are most at risk for having a child with sickle cell anemia; couples of central or eastern European Jewish (Ashekenazi), Cajun, or Irish descent may be carriers of Tay-Sachs disease; and couples of Italian, Greek, Middle Eastern, southern Asian, or African descent may carry the gene for thalassemia, a red blood cell disorder.
- either parent is concerned about the effects of exposures they have had to radiation, medications, illegal drugs, infections, or chemicals
Meeting With a Genetic Counselor
Before you meet with a genetic counselor in person, you may be asked to gather information about your family history. The counselor will want to know of any relatives with genetic disorders, multiple miscarriages, and early or unexplained deaths. The counselor will also want to look over your medical records, including any ultrasounds, prenatal test results, past pregnancies, and medications you may have taken before or during pregnancy.
When you meet with the counselor, you'll go over any gaps or potential problem areas in your family or medical history. The counselor can help you understand the inheritance patterns of any potential disorders and help assess your chances of having a child with those disorders.
The counselor will distinguish between risks that every pregnancy faces and risks that you personally face. Even if you discover you have a particular problem gene, science can't always predict the severity of the related disease. For instance, a child with cystic fibrosis can have debilitating lung problems or, less commonly, milder respiratory symptoms.
If more tests are necessary, the counselor will help you set up those appointments and track the paperwork. When the results come in, the counselor will call you with the news and may ask you to come in for another discussion.
Genetic counselors can help you understand your options and adjust to any uncertainties you face, but you and your family will have to decide what to do next.
If you've learned before conception that you and/or your partner are at high risk for having a child with a severe or fatal defect, your options might include:
- pre-implantation diagnosis — when eggs that have been fertilized in vitro (in a laboratory, outside of the womb) are tested for defects at the 8-cell (blastocyst) stage, and only nonaffected blastocysts are implanted in the uterus to establish a pregnancy
- using donor sperm or donor eggs
- taking the risk and having a child
- establishing pregnancy and have specific prenatal testing
If you've received a diagnosis of a severe or fatal defect after conception, your options might include:
- preparing yourself for the challenges you'll face when you have your baby
- fetal surgery to repair the defect before birth (surgery can only be used to treat some defects, such as spina bifida or congenital diaphragmatic hernia, a hole in the diaphragm that can cause severely underdeveloped lungs. Most defects cannot be surgically repaired.)
- ending the pregnancy
For some families, knowing that they'll have an infant with a severe or fatal genetic condition seems too much to bear. Other families are able to adapt to the news — and to the birth — remarkably well.
Genetic counselors can share the experiences they've had with other families in your situation. But they will not suggest a particular course of action. A genetic counselor understands that what is right for one family may not be right for another.
Genetic counselors can, however, refer you to specialists for further help. For instance, many babies with Down syndrome are born with heart defects. Your counselor might encourage you to meet with a cardiologist to discuss heart surgery, and a neonatologist to discuss the care of a post-operative newborn. Genetic counselors can also refer you to social workers, support groups, or mental health professionals to help you adjust to and prepare for your complex new reality.
Finding a Genetic Counselor
Working with a genetic counselor can be reassuring and informative, especially if you or your partner have known risk factors. Talk to your doctor if you feel you would benefit from genetic counseling. Many doctors have a list of local genetic counselors they work with. You also can contact the National Society of Genetic Counselors for more information.
Reviewed by: Larissa Hirsch, MD
Date reviewed: September 26, 2016