Race for the Case answers

Summer 2021 case by Zeinah AlHalees, MD, and AlReem Al-Nabti, MD

An otherwise healthy 40-year-old male presented to the dermatology clinic with skin lesions on the right upper arm and right lateral lower leg. He reported the appearance of the lesions a few weeks after his return from a trip to Algeria. His review of systems was negative. On physical exam, two erythematous verrucous plaques were noted on the right upper arm and four ulcerated plaques in a sporotrichoid distribution were evident on the right lateral lower leg. There was no mucous membrane involvement, and no associated regional adenopathy. Parasitized macrophages in the dermis were identified on histopathology with the organisms highlighted by Giemsa stain and CD1a immunostaining. The specimen was also sent for PCR.

1. What is the diagnosis and causative agent?
   Answer: Leishmaniasis. A chronic infection caused by obligate intracellular parasitic protozoa of the genus Leishmania.

2. What is the vector responsible for disease transmission?
   Answer: Leishmania parasites are transmitted through the bites of infected female sandflies from the genera Phlebotomus and Lutzomyia.

3. This disease can be classified based on two different classification systems, mention each system with its components.
   Answer: Leishmania can be classified based on geographic region to “Old World” vs. “New World” Leishmaniasis, and can be classified based on its four major clinical patterns to (1) Cutaneous, restricted to the skin and seen more often in the Old World, (2) Mucocutaneous, affects both the skin and mucosa and occurs almost exclusively in the New World, (3) Diffuse cutaneous, mainly in the New World, and (4) Visceral, affects organs of the mononuclear phagocyte system, e.g. liver and spleen.

4. Mention two limitations in culturing the organism.
   Answer: (1) Specialized media are required for culturing Leishmania spp. e.g. Nicolle–Novy–MacNeal (NNM) media or chick embryo media, and (2) cultures are positive in only approximately 40% of cases.

5. What test is considered to be the most specific and sensitive in diagnosing the disease?
   Answer: PCR-based methods represent the most sensitive and specific diagnostic tests.

6. What are the indications for systemic treatment of the disease?
   Answer: “New World” Leishmaniasis, especially if L. braziliensis complex infection is suspected, or “Old World” cutaneous leishmaniasis in (1) an immunocompromised host (2) > 4 lesions of substantial size (e.g. >1cm) or individual lesion(s) measuring ≥ 5cm (3) markedly enlarged regional lymph nodes (4) involvement of the mucosa, face, ears, genitalia, skin over joints.

References

1. Bolognia J, Schaffer JV, Cerroni L. Dermatology. 4th edition ed: Philadelphia, Pa.: Elsevier; 2018 9th November 2017. 2880

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