Changes

==Causes==

==Causes==

May be a primary condition or appear secondary to some chronic tissue destructive process

May be a primary condition or appear secondary to some chronic tissue destructive process such as:

*an infectious process elsewhere in the body

*an infectious process elsewhere in the body

*a result of sustained antigenic stimulation, eg repeated injections with an antigenic substance or production of excessive antibody by leukocytes

*sustained antigenic stimulation, eg repeated injections with an antigenic substance or production of excessive antibody by leukocytes

==Gross Pathology==

==Gross Pathology==