Bacillary angiomatosis: A bacterial infection due to a cat scratch most often seen today in people with HIV. The disease characteristically presents with swollen lymph nodes (lymphadenitis), sore throat, fatigue, and fever, chills, sweats, vomiting, loss of appetite, and weight loss. There is usually a little bump (a papule) which may be pus-filled (a pustule) at the site of the scratch. Then more nodules appear on and under the skin. As the number of nodules increases, patients get sicker.

In normal people the disease is self-limited and usually goes away by itself in a few weeks. It can also be treated with antibiotics.

In persons with HIV/AIDS the disease can cause severe inflammation of the brain, bone marrow, lymph nodes, lungs, spleen and liver. The disease can be fatal in persons with HIV. It can be easily treated with antibiotics such as erythromycin and doxycycline. Treatment is given until the skin lesions resolve, usually in 3 to 4 weeks.

Bacillary angiomatosis is so characteristic today of AIDS that it is an AIDS defining disease, according to the CDC (Centers For Disease Control).

A cat carrying the microbe does not show symptoms. It is not necessary to get rid of the cat. If someone in the household is at high risk, a test to detect the infection can be done and the cat can be treated.

The disease is caused by a bacterium called Rochalimaea henselae, which was reclassified as Bartonella henselae, named for Diane Hensel, a microbiologist. Bacillary angiomatosis has also been called cat scratch disease, cat scratch fever, regional lymphadenitis, and benign lymphoreticulosis.