Does isopathic phenomenon occur in leprosy?

Twenty-five patients of leprosy classified according to the criteria of Ridley and Jopling (1966) were studied to verify the existence of isopathic phenomenon, using lepromin and autoclaved BCG as antigens. BCG as well as lepromin injection sites showed tuberculoid granulomas in all the cases of tuberculoid, borderline tuberculoid, mid-borderline and indeterminate leprosy. In lepromatous and borderline lepromatous cases BCG injection sites showed infiltration of foam cells containing AFB and foci of epithelioid cells, while lepromin injection sites showed infiltration of foam cells containing AFB only. These findings in the present study do not support the occurrence of isopathic phenomenon in leprosy with BCG.