Involves not only shins, but also calves. Concentrated on the lower third of the legs. Depressed scars or pigmentation due to previously active lesions. Cause is unknown in cases of nodular vasculitis with a negative tuberculin skin test reaction. Look for evidence of active or previous infection.
Skin biopsy An excisional biopsy containing adequate subcutaneous fat is recommended.
Special stains for bacterial, fungal and acid-fast organisms, as well as tissue for culture of these organisms, are generally obtained. Polymerase chain reaction testing of tissue for Mycobacterium tuberculosis DNA may be a helpful confirmatory test. Caseationlike necrosis may also be seen. Vasculitis is not always identified and is not requisite for the diagnosis. Nodular vasculitis with a negative tuberculin skin test.