What is Metaphyseal Chondrodysplasia, Jansen Type?
Metaphyseal Chondrodysplasia, Jansen Type is a progressive and rare genetic syndrome that 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 date.
This syndrome is also known as:
Metaphyseal Chondrodysplasia, Murk Jansen Type
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 that 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.
Possible clinical traits/features:
Hip contracture, Hypercalciuria, Hypercalcemia, Short ribs, Hypophosphatemia, Hypoparathyroidism, Hypertelorism, Hyperphosphaturia, Metaphyseal chondrodysplasia, Metaphyseal cupping, Osteopenia, Micrognathia, Micromelia, Nephrocalcinosis, Narrow chest, Misalignment of teeth, Knee flexion contracture, Increased bone mineral density, Abnormal calcium-phosphate regulating hormone level, Bowing of the long bones, Brachydactyly, Craniofacial hyperostosis, Severe short stature, Clubbing of fingers, Clinodactyly of the 5th finger, Elevated alkaline phosphatase, Choanal stenosis, Choanal atresia, Brachycephaly, Prominent supraorbital arches in adult, Thick skull base, Waddling gait, Short long bone, Proptosis, Frontal bossing, Autosomal dominant inheritance, Sensorineural hearing impairment, Pathologic fractures.
How is it diagnosed?
To find out if someone has a diagnosis of Metaphyseal Chondrodysplasia, Jansen Type, it is important to have a consultation and evaluation with a clinical genetic specialist. Specialists may also suggest specific genetic testing or other types of tests to help reach a diagnosis. FDNA’s AI technology can help speed up the diagnostic process by analyzing facial features and other health information.
