Cat-scratch disease (CSD) is a bacterial zoonotic disease caused by the bacterium Bartonella henselae. In well-described cases, a blister or papule may be noted at the site where the bacterium was inoculated (typically, the site of a bite, scratches, or lick from a cat), followed several days later by subsequent regional lymphadenopathy. Low-grade fever and discomfort at the lymph node site are common. Affected lymph nodes may become purulent and spontaneously erupt.
Although CSD is usually self-limited, more serious manifestations can occur weeks or months after initial onset. These include granulomatous lesions of the liver or spleen, encephalopathy (including seizures, coma, and combative behavior), neuroretinitis, endocarditis, and osteomyelitis.
In persons with impaired immune responses, such as HIV-positive patients and persons on immune suppressive drug therapy, signs may be significantly modified and may persist indefinitely depending on the extent of immune suppression. Persistent bacteremia and significant recurrent fever are likely. In persons with CD4 T-lymphocyte counts below 100, lymph node swelling may not be apparent; however, angiomatous lesions involving the skin, viscera or other tissues (bacillary angiomatosis) may develop. Untreated Bartonella infections in immune impaired persons may be life-threatening.