Jansen's metaphyseal chondrodysplasia

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[edit | edit source]

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[edit | edit source]

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[edit | edit source]

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[edit | edit source]

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[edit | edit source]

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.