In this age of international travel it is necessary for dermatopathologists to be familiar with the appearances of all cutaneous infections, including those which are sometimes dismissed euphemistically as ‘infections of other countries’. Unfortunately, there is a bewildering number of such infections, making it difficult to commit to memory the details of all of them. Further problems result from the variable morphological appearances which a particular infectious agent may produce. Factors that may influence the histopathological features of a cutaneous infection include the numbers and virulence of the organism, the host’s immunological response, the stage of evolution of the disease, prior treatment, and the presence of secondary changes resulting from rubbing and scratching or superimposed further infection. Because certain infections may produce different histopathological changes under these various circumstances, it seems prudent to categorize the infections and infestations on an etiological rather than a morphological basis in the succeeding chapters. This traditional approach reduces unnecessary duplication.
*These infections are more suppurative than granulomatous; the latter component is not always present.
†‘Deep fungal infections’ is used here to include North American blastomycosis, sporotrichosis, chromomycosis, coccidioidomycosis, paracoccidioidomycosis, subcutaneous phycomycosis, and phaeohyphomycosis.
Morphological feature
Diseases to be considered
Palisading granulomas
Phaeohyphomycosis (p. 597); mycobacteriosis (p. 556); treponematosis (p. 574); sporotrichosis (p. 598); cryptococcosis (p. 590); coccidioidomycosis (p. 594); cat-scratch disease (p. 570); lymphogranuloma venereum (p. 571); schistosomiasis (p. 646)
Tuberculoid granulomas
Tuberculosis (p. 556); tuberculids (p. 559); tuberculoid leprosy (p. 564); syphilis [late secondary or tertiary] (p. 575); dermatophytosis [Majocchi’s granuloma] (p. 587); cryptococcosis (p. 590); alternariosis (p. 600); histoplasmosis (p. 595); keloidal blastomycosis (p. 605); protothecosis (p. 605); leishmaniasis (p. 635); acanthamebiasis (p. 635); echinoderm injury (p. 643); Vibrio and Rhodococcus infection (p. 562)
Suppurative granulomas
Atypical mycobacterial infections (p. 559); lymphogranuloma venereum (p. 571); blastomycosis-like pyoderma* (p. 553); actinomycosis* (p. 602); nocardiosis* (p. 601); mycetoma* (p. 600); cryptococcosis (p. 590); aspergillosis (p. 604) and other deep fungal infections† (p. 598); protothecosis (p. 605)
Histiocyte granulomas
Infections by atypical mycobacteria (p. 559); lepromatous leprosy (p. 565); leishmaniasis (p. 635); malakoplakia [Michaelis–Gutmann bodies in cytoplasm] (p. 571)
Histiocytes and plasma cells
Rhinoscleroma (p. 568); syphilis (p. 575); yaws (p. 577); granuloma inguinale [often abscesses also] (p. 567)
Plasma cells prominent
Syphilis (p. 575); yaws (p. 577); lymphogranuloma venereum (p. 571); chancroid (p. 568); visceral leishmaniasis (p. 638); trypanosomiasis (p. 635); arthropod bites [an uncommon pattern]; Vibrio infection (p. 552)
Eosinophils prominent
Arthropod bites (p. 661); helminth infestation (p. 646); cnidarian (coelenterate) contact (p. 642); subcutaneous phycomycosis (p. 603)
Neutrophils prominent
Impetigo [subcorneal neutrophils] (p. 548); ecthyma (p. 550); cellulitis (p. 552); erysipelas [prominent superficial edema also] (p. 551); granuloma inguinale [microabscesses] (p. 567); chancroid [superficial neutrophils] (p. 568); disseminated tuberculosis in AIDS patients (p. 559); erythema nodosum leprosum (p. 566); Lucio’s phenomenon (p. 566); anthrax (p. 567); yaws (p. 577) and pinta (p. 577) [both have intraepidermal abscesses]; blastomycosis-like pyoderma (p. 553); actinomycosis (p. 602); nocardiosis (p. 601); mycetoma (p. 600); fungal kerion (p. 585); phaeohyphomycosis (p. 597); aspergillosis (p. 604); mucormycosis [also infarction present] (p. 603); flea bites (p. 661)
Parasitized macrophages
Rhinoscleroma (p. 605); granuloma inguinale (p. 567); lepromatous leprosy (p. 565); histoplasmosis (p. 595); leishmaniasis (p. 635); toxoplasmosis [pseudocysts present] (p. 638); Penicillium infection (p. 604)
Parasitized multinucleate giant cells or foreign body reaction
Various fungal infections; protothecosis (p. 605); schistosomiasis (p. 646); Demodex mites within tissues; some other mite infestations
Superficial and deep dermal perivascular lymphocytic inflammation
Leprosy [indeterminate stage] (p. 564); secondary syphilis [often plasma cells present] (p. 575); arthropod bites (p. 661) and coral reactions (p. 642) [usually interstitial eosinophils also]; onchocercal dermatitis [microfilariae in lymphatics] (p. 648)
Psoriasiform epidermal hyperplasia
Chronic candidosis (p. 588); tinea imbricata (p. 584); chronic dermatophytoses [rare] (p. 585)
Pseudoepitheliomatous or irregular epidermal hyperplasia
Amebiasis (p. 634); toxoplasmosis [rare] (p. 638); mucocutaneous leishmaniasis (p. 637); schistosomiasis (p. 646); chronic arthropod bite reactions [rare] (p. 661); yaws (p. 577); rhinoscleroma (p. 568); granuloma inguinale (p. 567); blastomycosis-like pyoderma [oblique follicles and draining sinuses] (p. 553); tuberculosis [tuberculosis verrucosa and some infections by atypical mycobacteria] (p. 556); Vibrio infection (p. 552); certain deep fungal infections†; human papillomavirus infections (p. 619); milker’s nodule (p. 610) and orf (p. 611) [both of these may have thin, long rete pegs]; verrucous herpes/varicella lesions in HIV infection (p. 616)
Folliculitis and/or perifolliculitis
Syphilis [rare cases] (p. 575); dermatophytoses (p. 582); pityrosporum folliculitis (p. 593); pyogenic bacterial infections (p. 548); herpes simplex (p. 613); herpes zoster (p. 616); Demodex infestations (p. 653); larva migrans [eosinophilic folliculitis] (p. 649)
Vasculitis
Erythema nodosum leprosum (p. 566); Lucio’s phenomenon (p. 566); ecthyma gangrenosum (p. 550); necrotizing fasciitis (p. 552); meningococcal and gonococcal septicemia (p. 556); recurrent herpes [‘lichenoid lymphocytic vasculitis’] (p. 613); cytomegalovirus infection [endothelial cell inclusion bodies] (p. 618); rickettsial infections [lymphocytic vasculitis] (p. 572); spider bites (p. 652); papulonecrotic tuberculid (p. 559)
Tissue necrosis
Ecthyma gangrenosum (p. 550); necrotizing fasciitis (p. 552); diphtheria (p. 554); anthrax (p. 567); tularemia (p. 570); cat-scratch disease (p. 570); severe lepra reactional states (p. 566); scrofuloderma (p. 558); Mycobacterium ulcerans infections (p. 560); papulonecrotic tuberculid (p. 559); chancroid [superficial necrosis only] (p. 568); rickettsial infections [eschar present] (p. 572); herpes folliculitis (p. 615); mucormycosis (p. 603); gnat, spider, and beetle bites (p. 652); acute tick bites (p. 652); stonefish and stingray contact (p. 643); orf (p. 611); amebiasis (p. 634)
Epidermal spongiosis
Dermatophytoses (p. 582); candidosis (p. 588); cercarial dermatitis [eosinophils and neutrophils also] (p. 646); larva migrans (p. 649); chigger bites (p. 657); other arthropod bites; contact with moths of the genus Hylesia (p. 661); contact with beetles (p. 661); delayed reactions to cnidarians (p. 642); viral infections, including herpesvirus-6 and coxsackievirus
Intraepidermal vesiculation
Herpes simplex, herpes zoster, varicella [all three have ballooning degeneration and intranuclear inclusions] (p. 613); orf (p. 611) and milker’s nodule (p. 610) [both have pale superficial cytoplasm]; hand, foot and mouth disease (p. 626); erysipeloid [also superficial dermal edema] (p. 551); beetle bites (p. 661); certain other arthropod bites [may be bullous in hypersensitive persons]; dermatophytoses (p. 582); candidosis (p. 588)
Parasite in tissue sections
Helminth and arthropod infestations; certain injuries from forms of marine life
‘Invisible dermatoses’ (section stained with H & E appears normal at first glance)
Erythrasma (p. 554); pityriasis versicolor [spores and hyphae are usually easily seen] (p. 590); dermatophytoses [compact orthokeratosis, neutrophils in the stratum corneum or the ‘sandwich sign’ often present] (p. 585); pitted keratolysis [crateriform defects, pits or pallor of the stratum corneum are usually obvious, as are bacteria] (p. 555)
Spindle cell pseudotumors
Atypical mycobacteria (p. 559); histoid leprosy (p. 566); acrodermatitis chronica atrophicans (p. 579)
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