Metaphyseal Chondrodysplasia, Jansen Type

What is Metaphyseal Chondrodysplasia, Jansen Type?

It is a progressive and rare genetic syndrome which mainly affects the development of cartilage and bone in the body. As a progressive disorder symptoms worsen with age. There are just 20 cases of the syndrome reported worldwide to data.

What gene changes cause Metaphyseal Chondrodysplasia, Jansen Type?

Jansen disease is caused by changes to the PTH1R gene located on the short arm (p) of chromosome 3.

The majority of cases of the syndrome are de novo, or new and the first in a family. It is believed that the syndrome can be inherited in an autosomal dominant pattern.

In some cases, a genetic syndrome may be the result of a de-novo mutation and the first case in a family. In this case, this is a new gene mutation which occurs during the reproductive process.

In the case of autosomal dominant inheritance just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it onto each of their children. Syndromes inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation.

What are the main symptoms of Metaphyseal Chondrodysplasia, Jansen Type?

The symptoms of Jansen disease may vary between individuals in terms of their presentation and severity.

Due to abnormal bone development as a result of the syndrome most affected individuals have very short arms and legs, and a very short stature. Together these symptoms are known as short-limbed dwarfism.

The abnormal development of cartilage may cause anomalies and issues with the hands and feet also. This can also include a stiffening and swelling of the joints which affects walking. Over time affected individuals may develop the hardening of their bones, most notably in the back of their head, a development which can lead to blindness and/ or deafness.

An abnormally high level of calcium in the blood is also a feature of the syndrome.
Unique facial features of the syndrome include a very small jaw, a high arched palate of the mouth and widely spaced eyes.

How does someone get tested for Metaphyseal Chondrodysplasia, Jansen Type?

The initial testing for Metaphyseal Chondrodysplasia, Jansen Type can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow.

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.

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