Jansen's metaphyseal chondrodysplasia

Jansen's metaphyseal chondrodysplasia, abbreviated JMC, is an extremely rare disease that results from ligand-independent activation of the type 1 parathyroid hormone receptor, PTH1R, due to one of three reported activating mutations. As of 2007 fewer than 20 cases had been reported worldwide. Only two families are known in which the disease was passed on: one from Texas, where it passed from a mother to her daughter, and one from Dubai, where a mother passed it to her two sons. Because the recorded cases are so few, what is known about the condition comes from a very small number of affected people and their families.