A clinical and histopathological study of histoid leprosy

Histoid leprosy (HL) is a rare variant of lepromatous leprosy presenting with well-defined smooth shiny papules and nodules. This can mimic many other dermatoses and can be missed clinically.

This is a retrospective 10-year study. Data were obtained and analyzed from case records of the urban leprosy clinic at the Government Medical College, Trivandrum, Kerala (India).

There were 17 cases of HL in this study. The male/female ratio was 16 : 1 and the 41-50-year-old age group accounted for the maximum number of cases (six, 35.29%); 11 cases (64.70%) were de novo cases of HL. Papules were the commonest skin lesions encountered (17, 100%), while the upper and lower limbs and trunk were the most common sites involved (11, 64.70%). Earlobe infiltration was seen in 10 cases (58.82%). Lepra reactions were seen in four (23.52%) cases. Deformity/disability occurred only in two cases (11.76%). The mean morphological index was 30.58%, while the mean bacteriological index was 5.17. Epidermal atrophy and a well-circumscribed dermal area packed with spindle-shaped histiocytes and positive for acid-fast bacilli were the main histopathological features seen.

The majority of cases in this study were de novo. HL can occur even when there is no history of inadequate or irregular treatment. Papules rather than nodules were the most common skin lesions seen. Earlobe infiltration was seen in the majority of cases unlike that reported in the literature. Lepra reactions are very rare in HL.