Jansen's metaphyseal chondrodysplasia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 17, 2016
StartJansen's metaphyseal chondrodysplasia

Jansen's metaphyseal chondrodysplasia is currently classified as an "extremely rare" disorder, with just 20 medically documented reported cases on record to date. Jansen metaphyseal chondrodysplasia is sometimes also called simply Jansen disease. It is also called Jansen's metaphyseal dysostosis and Murk Jansen type metaphyseal chondrodysplasia.

Contents

Definition & Facts

One of the chief symptoms, short-limbed dwarfism, often lumps this much rarer condition in with the more than 200 other possible causes for dwarfism. However, there are some additional symptoms that set Jansen's metaphyseal chondrodysplasia apart and must be identified in order to arrive at an accurate diagnosis.

Symptoms & Complaints

Since Jansen's metaphyseal chondrodysplasia will develop progressively as the individual grows older, symptoms may change or worsen and new symptoms can present at any time. Some of the most commonly reported symptoms include:

Causes

The cause of Jansen's metaphyseal chondrodysplasia is now known to be from a genetic mutation. The disorder can be either spontaneous or heritable. When heritable, it is considered autosomal dominant which means that an individual only needs to receive a copy of the mutated gene from one (not both) parents in order to develop the disorder.

Thanks to recent research, some information is now known about the specific gene involved in Jansen's metaphyseal chondrodysplasia. The gene that is most likely a trigger in most cases of the disorder (spontaneous mutation) is within chromosome 3.

The mutation disrupts production of a protein called PTH/PTHrP (parathyroid) receptor. This protein is supposed to regulate how much calcium is in the blood and prevent hypercalcemia. This is important because hypercalcemia is thought to be a cause for many of the symptoms of Jansen's metaphyseal chondrodysplasia.

Diagnosis & Tests

Because the genetic mutation that causes Jansen's metaphyseal chondrodysplasia affects calcium levels, physicians test for calcium levels in both the urine and the blood when Jansen's metaphyseal chondrodysplasia is suspected.

In addition to genetic testing and the tests described here, doctors still use the symptoms checklist as a diagnostic tool especially as Jansen's metaphyseal chondrodysplasia is progressive and presents worsening symptoms over time that need to be catalogued.

Treatment & Therapy

Treatment for Jansen's metaphyseal chondrodysplasia is primarily related to managing symptoms as they arise. Typically the treatment needs of an affected individual will change and shift as the disease itself progresses, requiring a multi-disciplinary team to coordinate treatment. Team members often include the following medical professionals:

Surgical treatment can often correct some of the discomfort associated with joint and bone abnormalities as the disease progresses. Physical therapy can also assist with more comfortable movement and increased mobility.

A newer treatment that shows promise is to prescribe bisphosphonates, a class of drugs more typically associated with treating osteoporosis, or brittle bone syndrome. Administering bisphosphonates to individuals with Jansen's metaphyseal chondrodysplasia can help halt the loss of bone mass and stave off bone fractures that commonly occur with the disorder.

Prevention & Prophylaxis

Since individuals diagnosed with Jansen's metaphyseal chondrodysplasia do not tend to suffer from intellectual disability, it is often possible to have a relatively normal, full life while undergoing various therapies and treatment to manage symptoms of the disease. Individuals and families that are affected can particularly benefit from social and vocational support services for the best quality of life.