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Skin-nontumor / Clinical Dermatology

Infectious disorders

Leishmaniasis

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
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● 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

Diagnosis
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● 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)

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

Clinical images
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Cutaneous and mucosal forms

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

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

Additional references
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● 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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