Additional markers for the type I reactional states of borderline leprosy.

The histological course of reaction in borderline leprosy has been described by Ridley and Radia. They are dermal edema, dilatation of the lymphatics, swelling of the granulomas, changes in the concentration and distribution of lymphocytes and giant cells, maturity of the histiocytes, and presence of neutrophils. New markers for the condition are spongiosis of the epidermal and follicular epithelium with exocytosis of mononuclear cells, parakeratosis, focal interface changes with occasional individual cell necrosis of keratinocytes, and lastly, follicular mucinosis. Recognition of this reaction is vital in the prevention of deformities secondary to nerve damage.