Is nodular vasculitis common? what is it?

Tender leg nodules: Nodular vasculitis or erythema induratum is probably a hypersensitivity immune reaction that is triggered by an infectious process. Tuberculosis is present in about 50% of cases. These tender leg nodules often ulcerate (open sores). This disease is fairly uncommon in western countries such as the U.S. And often responds to treatment if the underlying associated infection is known.

Nodular vasculitis: Nodular vasculitis is a skin condition characterized by crops of small, tender, erythematous nodules on the legs, mostly on the calves and shins. Miroscopically there are epithelioid granulomas and vasculitis in the subcutaneous tissue, making it a form of panicullitis. Most of these cases are now thought to be manifestation of tuberculosis and indeed they respond well to anti-tuberculous treatmen.