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Bacterial Infections
(toxins and their relationship to variations in histologic patterns)
The reactions of the skin to local infections depend
in part on the pathogenicity of the organism. Two basic categories include the suppurative processes and the granulomatous processes. In suppurative processes, antigen-antibody reactions and activated complement have important roles. In granulomatous processes, the immune response at the histologic level is mediated in patterns in which epithelioid histiocytes are clustered; it is mediated at a cellular level.
The nature of the reaction, and the histologic response, to a bacterial infection is greatly influenced by the respective toxins. For example, pseudomonas septicemia often is
associated with areas of cutaneous necrosis, but the cellular response in the skin usually is remarkably cell-poor. In the areas of necrosis, the tissue is acellular and small vessels contain thrombi; organisms form
basophilic sheaths about the vessels (S11C11P6-1 & 2).
A superficial staphylococcal infection usually evokes a neutrophilic response in the skin. For particular types, the respective toxin can produce lysis of intercellular bridges in the
upper portion of the epidermis, or at the interface between the viable epidermis and the keratin layer (S11C11P6-3 & 4); the
response resembles the patterns of an auto-immune disease, pemphigus foliaceus.
Granulomatous Bacillary Perifolliculitis
Granulomatous bacillary perifolliculitis is an undocumented disorder characterized by perifollicular and follicular, suppurative and granulomatous, inflammation. Some of the activated
histiocytes of the infiltrates contain small Gram + cocco-bacillary forms (S11C11aP6a-1-5). The nature of the organism has not
been established by culture in any of the cases in my collection. Multiple sections may be required to demonstrate a connection between an involved follicle and the zones of suppurative, granulomatous inflammation
in the adjacent dermis.
Rhinoscleroma
Rhinoscleroma is a chronic infection of the nasal cavity caused by a Gram negative bacteria, Klebsiella rhinoscleromatis. It is characterized by diffuse infiltrates of foamy
histiocytes (S11C11bP6b-1-4) with an admixture of plasma cells. The infiltrates also contain the products of plasma
cells, Russell bodies.
Lues
Syphilis is a spirochaetal infection (treponema pallidum). It is manifested in stages, including the primary lesion (chancre) (S11C12P7-1-3), a secondary stage in which cutaneous lesions are multiple (renal and hepatic involvement also may be a feature) (S11C12P7-6), and a tertiary stage characterized by visceral (i.e. , cardio-vascular, and/or central nervous system) as well as
cutaneous, soft tissue, or osseous lesions. Although commonly cited as an antigen-antibody reaction, the histologic features are those of a cell-mediated response. Immune complexes have been cited as having a role
in the manifestations of secondary syphilis. In secondary lues, the reaction patterns in the superficial unit of the skin are commonly pityriasic in character, but for some examples (perhaps more advanced [i.e.,
older] lesions), the changes are lichenoid (S11C12P7-5); in some examples, they qualify as senescent lichenoid patterns. In
tertiary syphilis, the manifestations tend to be granulomatous.
Lesions of secondary lues commonly are characterized by band-like infiltrates of lymphocytes
and histiocytes in the papillary dermis and by migration of the infiltrates into a hyperplastic basal unit of the epidermis. In this combination, the patterns qualify as pityriasic and the epidermal infiltrates are rich in migratory histiocytes (S11C13P8-1-6). It is of interest that organisms, when identified in such lesions, are found not only in the dermis but also in
the epidermis (i.e., the migratory histiocytes are found in the same areas as the organisms) (S11C13P8-6). For some examples,
the basal unit is eroded by the effects of the inflammatory infiltrates; the patterns then become lichenoid. Plasma cells are variable in number in the band-like infiltrates (S11C13P8-5), usually being found in the perivascular components. They are sometimes most numerous in the perivascular
infiltrates in the deeper portions of the reticular dermis.
Along vessels of the reticular dermis, inflammatory infiltrates generally are prominent. In some examples of secondary lues, the infiltrates have a granulomatous component (S11C13P8-4).
Granuloma Inguinale
Granuloma inguinale is a infectious disease caused by a Gram negative bacillus. The disease mostly affects the genital areas and surrounding skin. Organism are found in the cytoplasm
of histiocytes; they often are referred to as Donovan bodies.
The epidermis, over a lesion, is hyperplastic. Dense infiltrates of inflammatory cells are present in the upper portion of the dermis and press upon the epidermis; they are composed
of sheets of activated histiocytes and focal collections of neutrophils. At the deep margin of such lesions, the infiltrates are rich in lymphocytes and plasma cells. The infiltrates, although rich in histiocytes,
are not truly granulomatous. The diagnosis depends upon the identification of intracellular organisms. The organisms can be identified with a Giemsa stain, but are small and must be searched for diligently.
With a silver stain, such as a Warthin-Starry stain, the organisms appear to be larger; they are more easily identified (S11C14P9-1-6).
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