THE MISSION OF THE JANSEN'S FOUNDATION IS TO BRING AWARENESS AND SUPPORT RESEARCH IN HOPES OF BRINGING ABOUT A CURE TO THIS DEBILITATING SKELETAL CONDITION.
JANSEN'S METAPHYSEAL cHONDRODYSPLASIA (JMC)
Jansen’s metaphyseal chondrodysplasia (JMC) is an extremely rare skeletal dysplasia characterized by progressive
growth plate abnormalities that affect most of the long bones.
JMC is usually diagnosed during childhood, based on a combination of radiographic and biochemical abnormalities. However, some patients are not diagnosed until adulthood.
The limbs of affected individuals typically show progressive changes that are caused by an abnormal regulation of chondrocyte growth and differentiation, eventually leading to short and bowed legs. X-rays during infancy show demineralization and rickets-like metaphyseal changes. Fraying of the metaphyses is seen during childhood. Long bones do not grow normally and result in severely reduced adult height.
There is usually severe hypercalcemia and hypophosphatemia despite normal or undetectable serum levels of PTH or PTHrP.
Four different mutations in the gene encoding the PTH/PTHrP receptor (PTHR1) have been identified in several unrelated Jansen's patients.
There are, at present, about 30 genetically confirmed cases of JMC, worldwide. Six of these cases are living here in America.