COMP and osteochondrodysplasia: In individuals with PSASH, their dramatically reduced limb lengthening appears to the result of an altered expansion of the extracellular matrix and longitudinal growth of the chondrocytes prior to ossification.17-20) Lamellar inclusion of the rER in the growth plate chondrocytes is the cytochemical hallmark for the PSACH phenotype, linking an endoplasmic reticulum storage disorder with the osteochondrodysplasia.