IPLab:Lab 11:Leishmaniasis

Clinical Summary

This 28-year-old white male presented to the dermatology clinic complaining of sores on his arms. On examination, two lesions measuring 0.7 to 1.5 cm in diameter were present on his right arm. These lesions showed central ulceration and a raised, indurated margin surrounding the ulcer. The lesions had developed over approximately one month. The patient had applied topical antibiotics, which had no effect. The patient had recently returned from a World Wildlife Fund study site in the Amazon region of Brazil, where he had been conducting field research in the rain forest. A biopsy was taken from the raised edge of one of the ulcers.

Images

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  In this photograph of the skin lesion seen in this patient, note the raised edges (arrows) and the ulcerated center.
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  This is a low-power photomicrograph of the biopsy taken from this skin lesion. The ulcerated surface is at the top. Note that the specimen is heavily infiltrated with inflammatory cells.
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  This is a higher-power photomicrograph of this biopsy. The ulcerated surface is seen on the top of the section. Again, note that the specimen is heavily infiltrated with inflammatory cells.
• 
  This high-power photomicrograph of the biopsy specimen shows more clearly the heavily infiltrate of inflammatory cells. Note the small blue structures inside the inflammatory cells (arrows).
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  This is a high-power photomicrograph of an inflammatory cell containing cytoplasmic organisms (arrows).
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  This is a high-power photomicrograph of a touch prep made from the skin lesion at the time of biopsy. A single macrophage can be seen with intracytoplasmic leishmania organisms (arrows).

Study Questions

• How is leishmaniasis transmitted and why was this patient at risk for getting leishmaniasis?

Leishmania parasites are transmitted by the bite of an infected sand fly. Sand flies are common in Central and South America as well as in the Middle East, Southeast Asia, and Africa. Travelers can help prevent infection by using insect repellent -- especially at night when sand flies are out biting.

• In what host cells do the parasites grow and how do they tolerate this hostile environment?

Leishmania amastigotes grow inside macrophage phagolysosomes. They have special glycoconjugates on their surface which help them resist attach by complement, help them bind to and be phagocytosed by macrophages, and help protect them from free radical damage inside the phagolysosomes. Leishmania amastigotes also have a special proton-transporting ATPase that helps them survive the high acidity of the phagolysosome.

• The patient had simple cutaneous leishmaniasis. What other clinical forms of leishmaniasis exist?

Patients can also get mucocutaneous leishmaniasis or visceral leishmaniasis depending on the species of leishmania organism causing the infection.

• If the biopsy had shown only a granulomatous inflammatory response but no organisms, what other infectious diseases would be in the differential diagnosis?

Blastomyces, Mycobacterium ulcerans, Sporothrix schenckii.

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An infiltrate is an accumulation of cells in the lung parenchyma--this is a sign of pneumonia.