Liver lesions in experimental lepromatoid leprosy of the armadillo. A histopathologic study

A retrospective study of liver lesions was made in 13 armadillos infected intracutaneously with 10(7) M. leprae from the same inoculum, to evaluate the pathogenesis of the experimental disease. Survival times ranged from 13 to 55 months. In seven armadillos the liver lesions were markedly less severe than in six of these animals. The extent of the lesions was unrelated to the duration of the infection and was interpreted as reflecting individual differences in resistance. In contrast to man, leprosy bacilli were found in the liver cells of both groups of armadillos but to a lesser extent in those of the more resistant armadillos. The latter also had no obvious changes in the liver tissue except for round cell infiltration and prominent Kupffer's cells which contained M. leprae. These lesions can be compared to indeterminate leprosy in humans. The lesions in the more susceptible (lepromatoid) armadillos were initiated in Kupffer's cells. Later, large collections of bacillated macrophages infiltrated the liver lobules. The liver cells heavily loaded with M. leprae developed a pale granular cytoplasm which became foamy in the late lesions. In three of the lepromatoid livers, lesions compatible with erythema nodosum leprosum were seen.