Mucopolysaccharidosis (MPS) Type IV
When a child begins to show signs such as slowed growth, joint abnormalities, or spinal changes, it often leads to more questions than answers. For many families, the path to understanding these symptoms can be long and confusing, especially when they do not fit a familiar diagnosis. In some cases, these early signs may point to a rare metabolic condition known as MPS IV, or Morquio syndrome.
This article provides a comprehensive overview of this condition. It covers how the disease presents, how it is diagnosed, and what treatment and support options are currently available. Whether you are a caregiver or someone personally affected, you will find medically grounded and accessible information to help guide your next steps.
What is Mucopolysaccharidosis Type IV?
Mucopolysaccharidosis Type IV (MPS IV), commonly referred to as Morquio Disease, is a rare inherited lysosomal storage disorder. The condition is caused by a deficiency in enzymes responsible for breaking down certain glycosaminoglycans (GAGs), such as keratan sulfate and chondroitin-6-sulfate. These substances accumulate in the body and lead to progressive damage, especially in bones, cartilage, and connective tissue.
According to Orphanet, there are two main subtypes of MPS IV:
- MPS IVA (Morquio A): Caused by a deficiency in the enzyme galactosamine-6-sulfatase (GALNS)
- MPS IVB (Morquio B): Caused by a deficiency in beta-galactosidase (GLB1)
Unlike many other types of MPS, cognitive function is typically not affected in MPS IV.
Symptoms of Morquio Disease
Symptoms of this disease usually appear in early childhood, often between the ages of 1 and 3. Affected children may appear healthy at birth, but progressive skeletal changes quickly become noticeable.
As stated by the Genetic and Rare Diseases Information Center (GARD) common symptoms include:
- Disproportionately short stature and slowed growth
- Abnormal spine curvature (kyphosis or scoliosis)
- Abnormal shape of end part of bones
- Joint laxity or stiffness
- Knock knees and a waddling gait
- Chest abnormalities (pectus carinatum)
- Frequent respiratory infections and breathing problems
- Hearing loss and, in some cases, cloudy corneas
- abnormality of the dental enamel
- Valvular abnormality
- Coarse facial features
- Hip abnormalities
Despite these challenges, intellectual development remains normal in most cases, allowing affected individuals to participate fully in school and social life.
How the diagnosis is made
Early and accurate diagnosis is critical to manage MPS IV effectively. The diagnostic process includes as outlined by Orphanet:
- Clinical examination based on physical signs and developmental history.
- Urine analysis to detect elevated levels of keratan sulfate.
- Enzyme activity testing in blood or skin cells to confirm reduced GALNS or beta-galactosidase levels.
- Genetic testing to identify pathogenic mutations in the GALNS or GLB1 gene.
- Imaging studies, such as X-rays or MRI scans, to assess skeletal abnormalities.
Prevalence worldwide
This condition is a rare inherited disorder. The estimated prevalence ranges from 1 in 250,000 to 1 in 300,000 live births worldwide according to Medline Plus. It affects both males and females equally and occurs across all ethnic backgrounds, although certain founder mutations have led to higher rates in specific populations.
Prognosis and Life Expectancy
The prognosis for MPS IV depends on the severity of the disease and how early treatment begins. As stated by Medline Plus, Individuals with severe forms of the disease often face a significantly shortened lifespan, with survival sometimes limited to late childhood or the teenage years. In contrast, those with milder variants typically reach adulthood, though their overall life expectancy is still reduced compared to the general population. Research indicates that spinal cord compression and airway obstruction are among the leading causes of mortality in this condition.
Quality of life can be strongly improved through:
- Early diagnosis
- Multidisciplinary treatment
- Regular follow-up and symptom management
Treatment Options
Enzyme Replacement Therapy (ERT)
As described by Sawamoto et al. (2020) for individuals with MPS IVA, an enzyme replacement therapy is available that supplements the missing enzyme responsible for breaking down certain glycosaminoglycans. This therapy is typically administered via weekly intravenous infusions and aims to reduce the accumulation of storage materials in the body.
Clinical studies have demonstrated that enzyme replacement can:
- Improve physical endurance (as measured by walking tests)
- Support respiratory stability
- Reduce the levels of harmful glycosaminoglycans in the urine
Currently, no enzyme replacement therapy is approved for MPS IVB, though research into potential treatments is ongoing.
Supportive Care and Monitoring
Beyond enzyme therapy, supportive care is essential for maintaining mobility, managing complications, and improving quality of life. According to Sawamoto et al. (2020) this typically includes:
- Orthopedic interventions, such as spinal or limb surgeries, to address skeletal deformities
- Physical and occupational therapy to preserve movement and independence
- Respiratory care, including sleep apnea management and breathing support devices
- Hearing and vision support, where needed
- Cardiac and pulmonary monitoring as part of routine follow-up
Patients benefit most from a multidisciplinary team approach, including specialists in genetics, orthopedics, pulmonology, cardiology, physiotherapy, and psychosocial care.
Living with Morquio Disease – Your Support through Saventic Care
Living with this condition presents unique challenges, but with the right support, individuals can lead active and fulfilling lives. At Savenic Care, we specialize in rare diseases like Morquio syndrome, offering access to diagnostics and clinical studies.
Do you suspect having MPS IV or another Rare Disease? You can use our free Risk Check for Rare Diseases. Just fill out our Patient Form and we do the rest. Get your secured analysis today, powered by AI and reviewed by our team of medical experts.
Sources:
- Genetic and Rare Diseases Information Center (GARD). Mucopolysaccharidosis type 4. https://rarediseases.info.nih.gov/diseases/12562/mucopolysaccharidosis-type-4
- Medline Plus. Mucopolysaccharidosis type IV https://medlineplus.gov/genetics/condition/mucopolysaccharidosis-type-iv/
- Orphanet. Mucopolysaccharidosis type 4. https://www.orpha.net/en/disease/detail/582
- Sawamoto, K., Álvarez González, J. V., Piechnik, M., Otero, F. J., Couce, M. L., Suzuki, Y., & Tomatsu, S. (2020). Mucopolysaccharidosis IVA: Diagnosis, Treatment, and Management. International Journal of Molecular Sciences, 21(4), 1517. https://doi.org/10.3390/ijms21041517