Page 177 - Textbook of Pathology, 6th Edition

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CHAPTER 6

Figure 6.33 Tuberculoid leprosy (TT). Granuloma eroding the basal layer of the epidermis. The granuloma is composed of epithelioid cells with Inflammation and Healing
sparse Langhans’ giant cells and lymphocytes.

ii) Borderline lepromatous (BL) form shows predominance Anti-leprosy vaccines have been developed and are
of histiocytes, a few epithelioid cells and some irregularly undergoing human trials but since the incubation period of
dispersed lymphocytes. Numerous lepra bacilli are seen. leprosy is quite long, the efficacy of such vaccines will be
iii) Mid-borderline (BB) or dimorphic form shows sheets known after a number of years.
of epithelioid cells with no giant cells. Some lymphocytes
are seen in the peri-neurium. Lepra bacilli are present, SYPHILIS
mostly in nerves. Syphilis is a venereal (sexually-transmitted) disease caused

4. Indeterminate leprosy: by spirochaetes, Treponema pallidum. Other treponemal
The histopathologic features are non-specific so that the diseases are yaws, pinta and bejel. The word ‘syphilis’ is
diagnosis of non-specific chronic dermatitis may be made. derived from the name of the mythological handsome boy,
However, a few features help in suspecting leprosy as Syphilus, who was cursed by Greek god Apollo with the
under: disease.
i) Lymphocytic or mononuclear cell infiltrate, focalised
particularly around skin adnexal structures like hair Causative Organism
follicles and sweat glands or around blood vessels. T. pallidum is a coiled spiral filament 10 μm long that moves
ii) Nerve involvement, if present, is strongly supportive actively in fresh preparations. The organism cannot be
of diagnosis. stained by the usual methods and can be demonstrated in
iii) Confirmation of diagnosis is made by finding of lepra the exudates and tissues by:
bacilli. 1. dark ground illumination (DGI) in fresh preparation;
2. fluorescent antibody technique;
Clinical Features 3. silver impregnation techniques; and
4. PCR as a research method.
The two main forms of leprosy show distinctive clinical The organism has not been cultivated in any culture
features: media but experimental infection can be produced in rabbits
1. Lepromatous leprosy: and chimpanzees. The organism is rapidly destroyed by cold,
i) The skin lesions in LL are generally symmetrical, heat, and antiseptics.
multiple, slightly hypopigmented and erythematous
macules, papules, nodules or diffuse infiltrates. The nodular Immunology
lesions may coalesce to give leonine facies appearance. T. pallidum does not produce any endotoxin or exotoxin. The
ii) The lesions are hypoaesthetic or anaesthetic but the pathogenesis of the lesions appears to be due to host immune
sensory disturbance is not as distinct as in TT. response.
2. Tuberculoid leprosy: There are two types of serological tests for syphilis:
i) The skin lesions in TT occur as either single or as a few treponemal and non-treponemal.
asymmetrical lesions which are hypopigmented and A. Treponemal serological tests: These tests measure
erythematous macules. antibody to T. pallidum antigen and are as under:
ii) There is a distinct sensory impairment. i) Fluorescent treponemal antibody-absorbed (FTA-ABS) test.