Overview
Mucopolysaccharidosis type 4B (MPS 4B), also known as Morquio B syndrome or Morquio disease type B, is a rare inherited metabolic disorder that belongs to a group of conditions called lysosomal storage diseases. In this condition, the body lacks enough of an enzyme called beta-galactosidase, which is needed to break down a specific sugar chain called keratan sulfate. When this sugar chain cannot be properly broken down, it builds up in cells throughout the body, especially in bones, cartilage, and connective tissues, causing progressive damage over time. The hallmark features of MPS 4B include skeletal abnormalities such as short stature, knock knees, abnormal curvature of the spine, and loose joints. The chest may develop an unusual shape, and the bones of the spine can become flattened or misshapen. Many patients also experience clouding of the cornea (the clear front part of the eye), hearing loss, and dental problems such as thin tooth enamel. Heart valve problems can also develop. Importantly, intelligence is usually normal in people with MPS 4B, which distinguishes it from some other types of mucopolysaccharidosis. MPS 4B can range from mild to severe. In severe cases, symptoms appear in early childhood and can lead to significant disability. In milder forms, symptoms may not become apparent until later in childhood or even adolescence. Currently, there is no specific enzyme replacement therapy approved for MPS 4B (unlike MPS 4A, which has an approved treatment). Management focuses on treating symptoms, preventing complications, and improving quality of life through surgeries, physical therapy, and regular monitoring by a team of specialists.
Also known as:
Key symptoms:
Short stature or growth failureKnock knees (legs bowing inward)Abnormal curvature of the spine (kyphosis or scoliosis)Flattened bones of the spineLoose or overly flexible jointsBarrel-shaped or protruding chestWaddling gait or difficulty walkingCloudy corneas affecting visionHearing lossThin or weak tooth enamel with frequent cavitiesHeart valve problemsNeck instability due to underdeveloped vertebraeHip problems or hip painBreathing difficultiesFatigue and reduced endurance
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Childhood
Begins in childhood, roughly ages 1 to 12
Treatments
No FDA-approved treatments are currently listed for Mucopolysaccharidosis type 4B.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for Mucopolysaccharidosis type 4B at this time.
New trials open frequently. Follow this disease to get notified.
Specialists
View all specialists →No specialists are currently listed for Mucopolysaccharidosis type 4B.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Mucopolysaccharidosis type 4B.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.How severe is my (or my child's) form of MPS 4B, and what can we expect over time?,How often should we have imaging of the spine, especially the neck, to check for instability?,Are there any clinical trials or experimental treatments available for MPS 4B?,What precautions need to be taken if surgery or anesthesia is ever needed?,What physical activities are safe, and which ones should be avoided?,How should we coordinate care among the different specialists involved?,Are there genetic counseling services available for our family to understand the risk for future children?
Common questions about Mucopolysaccharidosis type 4B
What is Mucopolysaccharidosis type 4B?
Mucopolysaccharidosis type 4B (MPS 4B), also known as Morquio B syndrome or Morquio disease type B, is a rare inherited metabolic disorder that belongs to a group of conditions called lysosomal storage diseases. In this condition, the body lacks enough of an enzyme called beta-galactosidase, which is needed to break down a specific sugar chain called keratan sulfate. When this sugar chain cannot be properly broken down, it builds up in cells throughout the body, especially in bones, cartilage, and connective tissues, causing progressive damage over time. The hallmark features of MPS 4B includ
How is Mucopolysaccharidosis type 4B inherited?
Mucopolysaccharidosis type 4B follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Mucopolysaccharidosis type 4B typically begin?
Typical onset of Mucopolysaccharidosis type 4B is childhood. Age of onset can vary across affected individuals.