A painless, non-itchy rash

Cutaneous leishmaniasis is a disease of the skin caused by an infection of the protozoa Leishmania.1,2 Though clinical presentations are diverse, cutaneous leishmaniasis commonly begins as a small papule that grows over time into a nodule before ulcerating.1-3 The disease...

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Cutaneous leishmaniasis is a disease of the skin caused by an infection of the protozoa Leishmania.^1,2 Though clinical presentations are diverse, cutaneous leishmaniasis commonly begins as a small papule that grows over time into a nodule before ulcerating.^1-3 The disease affects individuals worldwide, with an estimated prevalence of 12 million cases.² Over 90% of cases are seen in the Middle East, Brazil, and Peru; however, the disease has also been reported in Central Asia, Sub-Saharan Africa, India, and the United States.¹

Cutaneous leishmaniasis is divided into two categories—Old World and New World—based on the geographic location of infection. This distinction is important, as the 2 categories differ in Leishmania species, sandfly genus, clinical presentation, and prognosis.¹ Old World leishmaniasis, or infections endemic to the Middle East, Northern Africa, Asia, and the Mediterranean, are caused by the L tropica complex (eg, L major, L tropica, L aethiopica). New World leishmaniasis, or infections endemic to Central and South America, and Texas, are caused by the L mexicana complex (eg, L mexicana, L amazonesis, L pifanoi, L venezuelensis) as well as the L Vianna complex (eg, L panamensis, L guyanensis, L braziliensis).^3,4

The Leishmania protozoa is primarily transmitted through the bite of female sandflies; there are over 20 diverse species that cause disease.¹ When an individual is bitten by an infected sandfly, promastigotes are injected into the skin. Promastigotes are taken up by macrophages and transform into amastigotes. Amastigotes burst out of the macrophage to infect fellow macrophages. Histologically, amastigote-filled macrophages are a clear sign of disease.³ In acute lesions, these cells are seen alongside lymphocytes, epithelioid cells, plasma cells, and giant cells. The parasites are identified by their round shape, basophilic nature, and organization along the periphery of the macrophages in a “marquee sign.” With time, the number of infected macrophages drops, with a simultaneous increase in giant cells, epithelioid cells, and histiocytes.⁴

Clinically, all cases present with a small papule 1 to 2 weeks after the patient is bitten by an infected sandfly. The subsequent development of the papule depends on the infecting Leishmania species. Most patients present with 1 or 2 papules that enlarge before developing an ulceration at their center.⁵ These lesions typically maintain a thick and raised margin and remain painless unless secondary infection occurs. Ulceration is typical for the New World and Old World species, L major.² However, for Old World species L aethiopica and L tropica infection, instead of ulcerating, the papule may develop into a nodule or become hyperkeratotic.⁵ Most forms of cutaneous leishmaniasis resolve over time; however, exceptions include leishmaniasis recidivans, diffuse cutaneous leishmaniasis, mucocutaneous leishmaniasis, and post kala-azar dermal leishmaniasis.² Leishmaniasis recidivans, commonly caused by L tropica and L braziliensis, presents with recurrent papules around the edges of a healed lesion. Diffuse cutaneous leishmaniasis is a severe form of infection in which L amazonesis or L aethiopica parasites spread to create multiple lesions that can manifest indefinitely. This rare form typically does not occur unless an individual is already immunocompromised. Mucocutaneous leishmaniasis is caused when infection from the L vianna complex infects the mucosal membranes. Lesions form on the lips, and in the nose and mouth, and can lead to degradation of cartilage. Post kala-azar dermal leishmaniasis is a skin eruption following the resolution of visceral leishmaniasis. It consists of a hypopigmented maculopapular rash.^1,2

The clinical presentation of cutaneous leishmaniasis is often confused with infected insect bites, tropical ulcers, traumatic ulcers, pyoderma, foreign body granuloma, mycobacterial infections, fungal infections, malignant ulcers, and myiasis.⁵ Therefore, the diagnosis of cutaneous leishmaniasis relies on the appearance of amastigote-filled macrophages on a skin biopsy or tissue smear, or growth of the parasite in culture. New lesions are ideal for biopsy because chronic lesions have fewer parasites. In some cases, parasites may not be visible. Punch biopsies are recommended because they yield enough sample for a smear, histologic examination, culture, and polymerase chain reaction (PCR) analysis. PCR tests are sensitive when there are low numbers of parasites and are specific to different species of Leishmania.^1-3 A serologic test called the leishmanin skin test exists; however, it may not be useful for diagnosis because the test does not distinguish between past and present infection.^1,5

Treatment for cutaneous leishmaniasis varies by species of infection. Most Old World species, including L major and L tropica, resolve without treatment within 2 to 4 months or 6 to 15 months, respectively.¹ Conversely, most New World lesions, with the exception of L mexicana complex infections, require treatment to avoid development of mucocutaneous leishmaniasis.² Regardless, once the diagnosis of leishmaniasis is made, the patient should be referred to a leishmaniasis expert for treatment. Treatment is usually handled by infectious disease physicians in conjunction with the Centers for Disease Control and Prevention (Atlanta, GA). The main systemic treatment for cutaneous leishmaniasis and mucocutaneous leishmaniasis are parenteral pentavalent antimonial agents. First-line treatment for most New World lesions is intravenous or intramuscular sodium stibogluconate, 20 mg/kg/d for 20 days; doses should be lower for Old World lesions.⁵ A single course of sodium stibogluconate cures over 90% of New World  leishmaniasis.⁵ Adverse effects have been noted with injected antimonial use, including elevated amylase or lipase levels, and elevated liver function test results. As such, bloodwork and regular follow-up may be recommended.^1,2 New oral medications such as miltefosine have also been shown to be efficacious. Additional treatments include local heat therapy, cryotherapy, curettage, topical paromomycin, and oral imidazole drugs. However, studies demonstrate varying levels of efficacy.²

The patient in this vignette was diagnosed with New World cutaneous leishmaniasis. She was immediately referred to the local infectious disease experts for treatment. She was treated with sodium stibogluconate which led to the resolution of her infection.

Karen Resnick, BA, is a medical student at the Baylor College of Medicine, David Rizk, BA, is a medical student at the University of South Alabama, and Connie Wang, MD, is a dermatology resident at the Baylor College of Medicine.

References

1. Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012.
2. Bailey MS, Lockwood DN. Cutaneous leishmaniasis. Clin Dermatol. 2007;25:203-211.
3. Reithinger R, Dujardin JC, Louzir H, Pirmez C, Alexander B, Brooker S. Cutaneous leishmaniasis. Lancet Infect Dis. 2007;7:581-596.
4. Patterson JW, ed. Weedon’s Skin Pathology. 4th ed. London, UK: Churchill Livingstone; 2016.
5. Hepburn NC. Cutaneous leishmaniasis. Clin Exp Dermatol. 2000;25:363-370.