Light and electron microscopic study of ear cartilage in a case of relapsing polychondritis evolving under corticoid treatment.

Light and electron microscope studies of the ear cartilage in a patient with relapsing polychondritis (RP) under corticoid treatment are reported. Unilateral auricular deformation evolved without inflammatory epidoses and the lesions consisted mainly of marginal erosions filled with fine collagen fibrils and containing degenerating perichondrial cells in their basal parts. Degenerative cells were scattered throughout the perichondrium, but cartilage erosions only occurred when numerous cells were affected in a same area. Cartilage outside the eroded zones did not seem to be modified. Cartilage lesions thus appear to be a result of a chondrocyte renewal defect leading to loss of proteoglycans and elastic fibers, with only collagen remaining. These data suggest that inflammation is probably not the initial pathogenic process responsible for cartilage injury in RP, but that a metabolic defect in perichondrial cells might be involved.