Page 176 - Textbook of Pathology, 6th Edition

160 1. Upgrading reaction is characterised by increased cell- The main features in various groups are given below.
mediated immunity and occurs in patients of borderline 1. Lepromatous leprosy:
lepromatous (BL) type on treatment who upgrade or shift The following features characterise lepromatous polar
towards tuberculoid type.
leprosy (Fig. 6.32):
Histologically, the upgrading reaction shows an increase i) In the dermis, there is proliferation of macrophages
of lymphocytes, oedema of the lesions, necrosis in the with foamy change, particularly around the blood vessels,
centre and reduced B.I. nerves and dermal appendages. The foamy macrophages
are called ‘lepra cells’ or Virchow cells.
2. Downgrading reaction is characterised by lowering of ii) The lepra cells are heavily laden with acid-fast bacilli
SECTION I
cellular immunity and is seen in borderline tuberculoid (BT) demonstrated with AFB staining. The AFB may be seen
type who downgrade or shift towards lepromatous type. as compact globular masses (globi) or arranged in parallel
Histologically, the lesions show dispersal and spread of fashion like ‘cigarettes-in-pack’ (see Fig. 6.31).
the granulomas and increased presence of lepra bacilli. iii) The dermal infiltrate of lepra cells characteristically
does not encroach upon the basal layer of epidermis and
TYPE II: ERYTHEMA NODOSUM LEPROSUM (ENL). is separated from epidermis by a subepidermal
ENL occurs in lepromatous patients after treatment. It is uninvolved clear zone.
characterised by tender cutaneous nodules, fever,
iridocyclitis, synovitis and lymph node involvement. iv) The epidermis overlying the lesions is thinned out, flat
and may even ulcerate.
Histologically, the lesions in ENL show infiltration by 2. Tuberculoid leprosy:
neutrophils and eosinophils and prominence of vasculitis. The polar tuberculoid form presents the following
Inflammation often extends deep into the subcutaneous histological features (Fig. 6.33):
fat causing panniculitis. Bacillary load is increased.
Secondary amyloidosis may follow repeated attacks of i) The dermal lesions show granulomas resembling hard
ENL in leprosy. tubercles composed of epithelioid cells, Langhans’ giant
cells and peripheral mantle of lymphocytes.
Histopathology of Leprosy ii) Lesions of tuberculoid leprosy have predilection for
Usually, skin biopsy from the margin of lesions is submitted dermal nerves which may be destroyed and infiltrated by
for diagnosis and for classification of leprosy. The epithelioid cells and lymphocytes.
histopathologic diagnosis of multibacillary leprosy like LL iii) The granulomatous infiltrate erodes the basal layer of
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and BL offers no problem while the indeterminate leprosy epidermis i.e. there is no clear zone.
and tuberculoid lesions are paucibacillary and their diagnosis iv) The lepra bacilli are few and seen in destroyed nerves.
is made together with clinical evidence.
3. Borderline leprosy:
In general, for histopathologic evaluation in all suspected The histopathologic features of the three forms of
cases of leprosy the following broad guidelines should be borderline leprosy are as under:
followed: i) Borderline tuberculoid (BT) form shows epithelioid cells
cell type of granuloma; and plentiful lymphocytes. There is a narrow clear
nerve involvement; and subepidermal zone. Lepra bacilli are scanty and found in
bacterial load. nerves.

Figure 6.32 Lepromatous leprosy (LL). There is collection of proliferating foam macrophages (lepra cells) in the dermis with a clear subepidermal
zone.