Summary about Disease
Jansen's metaphyseal chondrodysplasia (JMC) is a rare genetic disorder characterized by severe skeletal abnormalities, particularly affecting the growth plates (metaphyses) of long bones. It results in short stature, bowed limbs, and abnormal bone development. The underlying cause is a mutation in a gene responsible for regulating bone growth and development.
Symptoms
Severe short stature
Bowed legs (genu varum) or knock knees (genu valgum)
Enlarged joints
Irregularly shaped bones, especially in the metaphyses
Hypercalcemia (elevated calcium levels in the blood)
Muscle weakness
Delayed motor development
Hearing loss may develop.
Progressive bone deformities.
Causes
JMC is caused by a dominant mutation in the PTH1R gene (parathyroid hormone 1 receptor). This gene provides instructions for making a receptor protein that binds to parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP). These hormones regulate calcium levels and bone development. The *PTH1R* mutation in JMC causes the receptor to be constantly activated, even in the absence of PTH or PTHrP, leading to excessive bone growth disruption and hypercalcemia.
Medicine Used
There is no cure for Jansen's Metaphyseal Chondrodysplasia. Treatment focuses on managing symptoms and complications. The following medicines may be used:
Bisphosphonates: To help manage hypercalcemia and improve bone density.
Calcimimetics: Medications that lower parathyroid hormone (PTH) levels.
Other Medications: Medications can be used for pain management, and supportive care.
Is Communicable
No, Jansen's Metaphyseal Chondrodysplasia is not communicable. It is a genetic disorder caused by a gene mutation and cannot be transmitted from person to person.
Precautions
Genetic Counseling: For families with a history of JMC, genetic counseling is recommended to understand the risk of recurrence and available reproductive options.
Monitoring Calcium Levels: Regular monitoring of serum calcium levels is crucial to manage hypercalcemia.
Orthopedic Management: Regular follow-up with an orthopedic specialist is essential to monitor and manage skeletal deformities.
Physical Therapy: Physical therapy can help improve muscle strength, range of motion, and mobility.
How long does an outbreak last?
Since Jansen's Metaphyseal Chondrodysplasia is not an infectious disease, the term "outbreak" does not apply. It is a chronic condition that is present from birth and lasts throughout the individual's lifetime.
Timeline of Symptoms
Infancy: Symptoms may be present at birth or become apparent in early infancy, with bone abnormalities and hypercalcemia.
Childhood: Short stature and skeletal deformities become more pronounced during childhood.
Adulthood: The condition persists into adulthood, with continued skeletal abnormalities, potential for joint pain, and ongoing management of hypercalcemia.
Progressive Throughout Life: JMC is a progressive condition, with skeletal deformities and other symptoms worsening over time.
Important Considerations
Multidisciplinary Care: Management requires a multidisciplinary team including geneticists, endocrinologists, orthopedic surgeons, and physical therapists.
Symptom Management: Focus on managing symptoms such as hypercalcemia, pain, and skeletal deformities.
Genetic Counseling: Provide genetic counseling to families for accurate information and family planning.
Quality of Life: Address psychosocial aspects and ensure optimal quality of life through supportive care and interventions.