Jansen's metaphyseal chondrodysplasia

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Jansen's metaphyseal chondrodysplasia
Synonyms	Metaphyseal chondrodysplasia, Jansen type
Pronounce	N/A
Specialty	N/A
Symptoms	Short stature, bowed legs, hypercalcemia, metaphyseal dysplasia
Complications	N/A
Onset	Infancy
Duration	Lifelong
Types	N/A
Causes	Mutations in the PTH1R gene
Risks	Family history of the condition
Diagnosis	Genetic testing, radiographic imaging
Differential diagnosis	Rickets, hypophosphatasia, Schmid metaphyseal chondrodysplasia
Prevention	N/A
Treatment	Symptomatic treatment, orthopedic surgery
Medication	N/A
Prognosis	Variable, depending on severity
Frequency	Rare
Deaths	N/A

Jansen's Metaphyseal Chondrodysplasia (JMC) is a rare, genetic skeletal disorder characterized by short stature, metaphyseal abnormalities, and endocrine dysfunction. It is named after the Dutch pediatrician Peter Jansen, who first described the condition in 1955.

Etiology

JMC is caused by mutations in the Parathyroid hormone receptor 1 (PTH1R) gene, which is involved in the regulation of calcium metabolism. The mutations lead to constitutive activation of the receptor, resulting in increased bone turnover and abnormal bone growth.

Clinical Features

Patients with JMC typically present in infancy with short stature, waddling gait, and deformities of the long bones. Other features may include hypercalcemia, hypercalciuria, and nephrocalcinosis. Some patients may also have endocrine abnormalities such as hypothyroidism and hypogonadism.

Diagnosis

The diagnosis of JMC is based on clinical features, radiographic findings, and genetic testing. Radiography typically shows metaphyseal widening and irregularity, particularly in the knees and wrists. Genetic testing can confirm the diagnosis by identifying a mutation in the PTH1R gene.

Treatment

There is currently no cure for JMC. Treatment is supportive and aims to manage symptoms and prevent complications. This may include physiotherapy for mobility issues, orthopedic surgery for bone deformities, and medication to manage hypercalcemia and other endocrine abnormalities.

Prognosis

The prognosis for individuals with JMC varies. Some individuals may have a normal lifespan with appropriate management, while others may experience significant morbidity and mortality due to complications such as renal failure.

See Also

• Metaphyseal dysplasia
• Parathyroid hormone
• Genetic disorder

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