A 45 year-old HIV-positive male presented with multiple red hemangioma-like lesions. Biopsy specimens show clusters of bacillithat stain positively with the Wahin-Starry stain. Which of the following could be the causative organism?
**Core Concept**
The patient's presentation is suggestive of bacillary angiomatosis, a condition characterized by the formation of vascular lesions due to an infection caused by Bartonella species. This condition is more common in individuals with compromised immune systems, such as HIV-positive patients.
**Why the Correct Answer is Right**
Bartonella species, particularly Bartonella henselae, are the causative agents of bacillary angiomatosis. These bacteria infect endothelial cells and cause the formation of vascular lesions, which are composed of clusters of bacilli that stain positively with the Warthin-Starry stain. The infection is thought to occur through the bites of infected fleas or ticks, which are the natural reservoirs of Bartonella species.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Bartonella species are not known to cause histoplasmosis, a fungal infection caused by Histoplasma capsulatum.
**Option B:** This option is incorrect because Plasmodium species are the causative agents of malaria, which presents with fever, chills, and anemia, but not with multiple red hemangioma-like lesions.
**Option C:** This option is incorrect because Leishmania species are the causative agents of leishmaniasis, a parasitic infection that presents with skin lesions, but not with the characteristic vascular lesions seen in bacillary angiomatosis.
**Clinical Pearl / High-Yield Fact**
Bacillary angiomatosis is a classic example of a "great imitator" disease, meaning that it can mimic other conditions such as Kaposi's sarcoma, pyogenic granuloma, or even histoplasmosis. A high index of suspicion and a thorough understanding of the clinical presentation and laboratory findings are essential for diagnosing this condition.
**Correct Answer:** C. Bartonella henselae.