Response by Dr. Fiallo and Dr. Nunzi
To the Editor:
We are responding to the letter from the Drs. Corcos with regard to our paper entitled "Histoid leprosy in early macular lepromatous leprosy: incidental finding or sign of augmented local immunity." The paper was a report on an untreated case of leprosy where three different lesions occurred: a) macular lesions of active lepromatous leprosy; b) a single macule with features of regressive leprosy; and c) histoid nodules.
The natural history of leprosy comes from the encounter of two players: Mycobacterium leprae and the human host (namely, his cell-mediated immunity). The unusual concomitance in an untreated patient of lesions belonging to different stages (active, regressive, histoid) of leprosy could be ascribed to: a) mutant forms of M. leprae responsible for either lepromatous macules and histoid nodules according to their genotypic features (even though spontaneous regression of a macule would remain unexplained); and b) the human host, by means of his cell-mediated immunity, contributing to active lepromatous lesions, regressive lepromatous lesions or histoid nodules on the grounds of his local immune competence.
In our paper we upheld the thesis of the local immunity supported by some evidence: a) spontaneous regression in an untreated patient is more likely a sign of effective host response rather than a consequence of a "less-infective" variant of M. leprae; b) the spontaneous regression of a lesion in our case occurred at the same time as the outbreak of histoid nodules; and c) the well-known occurrence of immune areas in patients with borderline lepromatous leprosy shows that tissue response to leprosy infection can be locally different.
The Drs. Corcos in their letter maintain that mutation of Hansen's bacilli is responsible for several unexplained findings in leprosy. Their thesis is stimulating, and we are grateful to them for their contribution. However, no evidence is currently available to support such a speculation or even make it possible to investigate it.
- Paolo Fiallo, M.D.
Enrico Nunzi, M.D.
CIRLEP
University of Genoa
Viale Benedetto XV, 7
1-16132 Genoa. Italy