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Skin-nontumor / Clinical Dermatology

Infectious disorders


Reviewer: Mowafak Hamodat, MB.CH.B, MSc., FRCPC, Eastern Health, St. Johns, Canada (see Reviewers page)
Revised: 24 August 2011, last major update July 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.

Clinical features

● Protozoal disease in all continents except Australia and Antarctica
● 1-2 million new cases per year worldwide
● Epidemics occur periodically in tropical regions of world; also infections in HIV+ patients
● Produces crusted, indurated papule that slowly enlarges and is self limited, as well as fatal systemic illness
● Disease is either cutaneous, mucocutaneous or visceral
● May may be misinterpreted as sarcoidosis, foreign body reaction, granulomatous rosacea and even granuloma annulare

● Cutaneous: usually restricted to face, scalp, arms or other exposed areas
● Localized, disseminated (if immune system doesn’t respond to invading parasites), recurrent (recidivans cutaneous) or post-kala azar (rare, years after visceral disease)

Mucocutaneous: usually New World disease of rural and jungle regions
● Occurs when primary infection with L. braziliensis becomes disseminated to upper respiratory tract, produces lesions of oral, pharyngeal or nasal mucosa with ulceration, mutilation or sometimes death

Visceral: also called kala azar; parasites throughout reticuloendothelial system, causing fever, malaise, hepatosplenomegaly, anorexia, pancytopenia, hypergammaglobulinemia
● Usually spares skin except for irregular areas of dark pigmentation (kala azar means “black sickness”)
● May cause death if untreated
● Broadly divided into “old world” (tropical and subtropical Asia, India, Africa and Mediterranean) and “new world” (Americas)
● Old world: usually Leishmania tropica complex
● New world: L. braziliensis complex and L. mexicana complex
L. braziliensis may also produce espundia, a destructive mucocutaneous form
● Human infection through bite of Phlebotomus sand fly (smaller than mosquitoes); rarely through blood contamination
● Clinical presentation and prognosis vary based on species, duration of infection and immune status of patient
● US infections primarily through travel and HIV infection

Life cycle


● Intradermal delayed hypersensitivity test (Montenegro); culture on NNN agar using smears from ulcer; also ELISA, DNA probes, PCR
● Also by identifying parasites on H&E or in smears, by culture on specialized media, by leishmanin intradermal skin test (Montenegro test), by fluorescent antibody tests using the patient's serum, or by PCR using species-specific primers (but PCR results can be false positive)
● Note: leishmanin test is usually negative in the forms with cell-mediated hyporeactivity, such as the diffuse cutaneous forms and the visceral form (kala-azar)


● Drugs for cutaneous forms (Expert Rev Anti Infect Ther 2010;8:419)
● Mucocutaneous and diffuse cutaneous forms may be refractory to treatment

Clinical images

Cutaneous and mucosal forms

Micro description

● Dermal granulomatous inflammation with prominent lymphocytes
● Histiocytes contain small oval organisms with bar shaped paranuclear kinetoplast

Micro images

Various images

Various images of cutaneous disease

Various images contributed by Professor Venna Maheshwar, Drs. Kiran Alam and Anshu Jain, J.N. Medical College, India:

Bone marrow aspirate smear of visceral leishmaniasis

Positive stains

● Weigert iron hematoxylin may stain parasites better than H&E or Giemsa
● Immunohistostain using G2D10 antibody is more sensitive than H&E

Additional references

Arch Pathol Lab Med 2002;126:471, U.S. Centers for Disease Control

End of Skin-nontumor / Clinical Dermatology > Infectious disorders > Leishmaniasis

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