“Bacillary Angiomatosis”. Causative organism is
**Core Concept**
Bacillary angiomatosis (BA) is a rare, acquired vascular disorder caused by Bartonella species, particularly Bartonella henselae and Bartonella quintana. It typically affects immunocompromised individuals, such as those with HIV/AIDS, and presents with skin lesions, fever, and night sweats.
**Why the Correct Answer is Right**
Bartonella species infect endothelial cells, leading to the formation of vascular proliferations and angiomatosis. The bacteria induce the production of angiogenic factors, promoting the growth of new blood vessels and resulting in the characteristic skin lesions. The causative organism, Bartonella henselae, is typically transmitted through cat scratches or bites, highlighting the importance of zoonotic transmission in this disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Bartonella species are not typically associated with tuberculosis or other mycobacterial infections. While both conditions can affect immunocompromised individuals, they have distinct microbiological and clinical presentations.
**Option B:** Histoplasma capsulatum is a fungus that causes histoplasmosis, a different disease characterized by respiratory symptoms, fever, and potentially disseminated infection in immunocompromised hosts.
**Option C:** Toxoplasma gondii is a protozoan parasite that causes toxoplasmosis, primarily affecting the central nervous system in immunocompromised individuals.
**Clinical Pearl / High-Yield Fact**
Bacillary angiomatosis should be considered in the differential diagnosis of skin lesions in immunocompromised patients, particularly those with a history of cat exposure or scratches.
**Correct Answer: C. Bartonella quintana.**