We separated PRSD from the other lesion grades because, while grades 1 to 4 appeared to form a continuum of a response, there was no obvious link between PRSD and these other lesion types. PRSD lesions were uniformly large, relatively unpigmented, and with extensive chronic inflammation, suggesting a slowly developing lesion. However, no small lesions which might be suspected to be an earlier stage were ever observed, suggesting that the initial changes leading to this lesion may occur very rapidly and:or may not be grossly evident on affected individuals. Thus, there is no clear link between the mild (presumably early) lesions that we observed and PRSD.