A 38-year-old woman comes to the office for evaluation of a skin lesion. It began as a pink papule on her right arm and has progressively enlarged over several weeks. The lesion is not pruritic or painful and has not been associated with fever or other systemic symptoms. The patient returned from a trip to Costa Rica 5 weeks ago. During her travel, she stayed at a beachside resort and hiked in the rainforest. Skin examination findings are shown below. Biopsy of the lesion reveals intracellular, round-oval protozoa with rod-shaped kinetoplasts. Which of the following most likely led to this patient's current condition?

Question

A 38-year-old woman comes to the office for evaluation of a skin lesion.  It began as a pink papule on her right arm and has progressively enlarged over several weeks.  The lesion is not pruritic or painful and has not been associated with fever or other systemic symptoms.  The patient returned from a trip to Costa Rica 5 weeks ago.  During her travel, she stayed at a beachside resort and hiked in the rainforest.  Skin examination findings are shown below.  Biopsy of the lesion reveals intracellular, round-oval protozoa with rod-shaped kinetoplasts.  Which of the following most likely led to this patient's current condition?

Quizplus · Accepted Answer

11ec160b_37ea_d252_9249_cb43c9ffe0ca_MD0001_00 Microscopy of this patient's skin lesion revealed intracellular protozoa with rod-shaped kinetoplasts, raising strong suspicion for cutaneous leishmaniasis, a parasitic disease endemic to the Middle East and Central and South America. Leishmania species are harbored by small mammals and transmitted to humans via bites from infected sand flies. The parasite subsequently matures within mammalian macrophages and can be visualized on biopsy as intracellular, round-oval amastigotes with rod-shaped kinetoplasts (see arrow). Cutaneous leishmaniasis is characterized by a chronic, enlarging, pinkish papule at the site of the bite that eventually develops into a nodule or plaque and ulcerates. Most cases occur on exposed areas of skin because sand fly bites cannot penetrate clothing. More serious mucosal or lymphatic Leishmania infections can also occur. (Choice B) Yaws, a spirochetal infection caused by Treponema pallidium subspecies, is transmitted by skin-to-skin (nonsexual) contact and is seen in Central America. Patients typically develop a painless papule that eventually ulcerates (similar to syphilitic chancre). However, this organism is a bacterium, not a protozoan. (Choice C) Sporothrix schenckii, a dimorphic fungus, grows in decaying plant matter and is transmitted to humans via subcutaneous inoculation. Manifestations include a papule at the site of inoculation and subsequent papules along proximal lymphatic drainage pathways. Histopathology demonstrates granulomas and cigar-shaped, budding fungus. (Choice D) Bacillus anthracis, a gram-positive bacterial infection, is often transmitted to humans due to cutaneous contact with infected animals or animal hides. Manifestations include a painless cutaneous papule that evolves over days into an ulcer with a black eschar. Histopathology would show extracellular, gram-positive rods. (Choice E) Mycobacterium marinum, an acid-fast bacterium, causes cutaneous infection after exposure to contaminated water (eg, fish tank). Patients typically develop a papule that ulcerates and scars. However, histopathology would not show intracellular protozoa. Educational objective: Leishmania species are obligate intracellular protozoa that mature in macrophages and can be identified on biopsy by the presence of rod-shaped kinetoplasts. They are transmitted to humans by infected sand flies and cause the clinical syndrome of cutaneous leishmaniasis, characterized by a chronic, pinkish papule that evolves into a nodule or plaque.

A 38-Year-Old Woman Comes to the Office for Evaluation of a Skin