Histology of the Fernandez reaction. An appraisal.

The early lepromin reaction was studied clinically and histologically in 38 leprosy patients. There was a quantitative and a qualitative difference in the character of the early inflammatory response to lepromin in the different groups of leprosy patients. In tuberculoid patients, the extent and degree of inflammation and the density of lymphocytic infiltration were maximal. In the polar lepromatous group, the inflammatory reaction was far less intense, and lymphocytes were scarce or absent. An intermediate histology was noted in the borderline and indeterminate groups of patients. In 11 patients with negative clinical reactions, the histology showed moderately dense lymphocytic infiltrations. The paucity of the clinical reaction could be due to the injection and localization of the antigen in the mid- and deep dermis. The correlation between early and late lepromin reactivity, both clinically and histologically, in the polar tuberculoid group and the polar lepromatous group was good. In the borderline and indeterminate groups, only the correlation between the early and late histological reactions to lepromin was good. The relationships between the early and late clinical reactions to lepromin showed marked variation. It is suggested that the early reaction is as good an indicator of lepromin reactivity as the late reaction in all forms of leprosy but only if it is assessed histologically.