This disease is rarely a primary one, being induced chiefly by syphilitic and tubercular inflammations, especially when there is deep ulceration extending down to the perichondrium. It occurs occasionally as a sequel of typhoid and also probably of typhus fever. It has usually a somewhat chronic course, but may be acute, and in either case it ends in the formation of pus under the perichondrium. The pus, accumulating under the perichondrium, cuts off the cartilage from its source of nutrition, and, just as in periostitis, this is usually followed by necrosis of the cartilage. The destruction of the cartilage may be a slow process, and there may be a kind of caries followed by necrosis. This disease is generally confined to one cartilage at' the outset, the cricoid being most frequently attacked, but it may extend to others. When suppuration has occurred the inflammation spreads to structures around, and we may have burrowing of the pus under the mucous membrane for some distance, or even outside the larynx among the structures of the neck.

The necrosed cartilage is, by degrees, separated from.the living. It is usually discharged into the larynx, but the pus sometimes forms an external opening through which the cartilage may pass. There is usually great deformity of the larynx, which may be partly due to the primary disease and partly to the collapse resulting from loss of the cartilage. When the cartilage is discharged it is generally found calcified or ossified, and it may be a question how far the calcification preceded the inflammation. Dietrich has suggested that, in the case of the cricoid, ossification may sometimes be the primary condition, and that the inflammation may be induced by the pressure of the hardened cartilage against the vertebral column.