Pathology of Histoid Leprosy

Dr Sampurna Roy MD               2022

Histoid leprosy is a rare well-defined variant of multibacillary lepromatous leprosy with specific clinical and histo-pathological features.

Macrocopically, the lesion consisted of well-defined smooth cutaneous papules, or subcutaneous nodules and plaques over normal skin.

Common sites include arms, dorsum of hands, thighs, on the lower part of the back and on the buttocks.

Microscopically, it is a well formed lesion surrounded by a pseudocapsule.

The main microscopic features include epidermal atrophy, a subepidermal grenz zone in some cases, spindle-shaped histiocytes and many macrophages in the dermis.

Some inflammatory cells may be present.

The spindle shaped cells are arranged in an intertwining pattern. Some polygonal shaped cells are present.

The lesion resembles a fibrohistiocytic tumour.

Wade Fite stain shows dense collection of acid fast bacilli.

Diagnosis of Histoid Leprosy can be easily missed as leprosy has been completely eradicated in many countries. This lesion can be misdiagnosed as a fibrohistiocytic tumour. 

History of foreign travel to endemic area is crucial in a suspected case of Histoid Leprosy.