Jansen's metaphyseal chondrodysplasia: a disorder due to a PTH/PTHrP receptor gene mutation.

Jansen's metaphyseal chondrodysplasia (JMC) is a rare genetic disorder that is characterized by short-limbed dwarfism and severe, agonist-independent hypercalcemia. An activating PTH/PTHrP receptor mutation that results in constitutive cAMP accumulation was recently identified in the genomic DNA of a patient with this disorder. These findings provide a plausible explanation for the abnormal regulation of growth-plate chondrocytes and mineral ion homeostasis in JMC, and may have significant implications for understanding the broader biological role of PTHrP and its receptor.