Cat-Scratch Disease

Within 3 to 10 days after a bite or scratch, most patients with cat-scratch disease develop an erythematous, crusted, painless papule (rarely, a pustule) at the scratch site.

Regional lymphadenopathy develops within 2 weeks. The nodes are initially firm and tender, later becoming fluctuant, and may drain with fistula formation. Fever, malaise, headache, and anorexia may accompany lymphadenopathy.

Cat-Scratch Disease

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CAVALLINI JAMES / BSIP/SCIENCE PHOTO LIBRARY

Unusual manifestations occur in 11 to 12% of patients and are more likely to occur in adults:

• Parinaud oculoglandular syndrome (conjunctivitis associated with palpable preauricular nodes) (accounts for approximately 50% of atypical cases)

• Neurologic manifestations (encephalopathy, seizures, neuroretinitis [causes acute unilateral vision loss], radiculitis, myelitis, paraplegia, cerebral arteritis) in 2%

• Hepatosplenic granulomatous disease in < 1%

Patients may also present with a fever of unknown origin. B. henselae is one of the more common causes of culture-negative endocarditis, usually in patients with predisposing valvular heart disease. In immunosuppressed patients, B. henselae can cause bacillary angiomatosis and peliosis hepatis. Severe disseminated illness may occur in patients with AIDS.

Lymphadenopathy subsides spontaneously within 2 to 5 months. Complete recovery is usual, except in severe neurologic or hepatosplenic disease, which may be fatal or have residual effects.

• Acute and convalescent serologic testing or polymerase chain reaction (PCR) testing

• Sometimes lymph node biopsy

Diagnosis of cat-scratch disease is typically confirmed by positive serum antibody titers (testing acute and convalescent sera 6 weeks apart is recommended) or PCR testing of samples from lymph node aspirates.

Because similar lymphadenopathy may be caused by other infections (eg, tularemia, mycobacterial infection, brucellosis, fungal infection, lymphogranuloma venereum), testing for those organisms may be done if the diagnosis is not clearly cat-scratch disease.

Lymph node biopsy may be done if cancer is suspected or if the diagnosis of cat-scratch disease needs to be confirmed. Diagnosis is suggested by characteristic histopathologic findings (eg, suppurative granulomas) or detection of organisms by immunofluorescence. Warthin-Starry silver stains also may be used to demonstrate the bacteria; the combination of the stain with immunohistochemistry is highly sensitive (1).

Immunocompromised patients and patients with systemic symptoms should also have blood cultures (which require prolonged incubation). Lymph node aspirates are rarely culture-positive. However, Bartonella species can be isolated from cultures of lymph node biopsy specimens. Special culture media are often required.

• Local heat and analgesics

• Antibiotics for immunocompromised patients and sometimes for patients with systemic disease

Treatment of cat-scratch disease in immunocompetent patients is with local heat application and analgesics for this typically self-limited disease. If a lymph node is fluctuant, needle aspiration usually relieves the pain.

Antibiotic treatment is generally not given for localized infection in immunocompetent patients. However, azithromycin may be given to potentially reduce the duration of symptoms and adenopathy (1) and to perhaps decrease the risk of systemic spread.

Antibiotic treatment is recommended for patients who are immunocompromised and generally given to patients with systemic disease. Azithromycin or doxycycline is commonly used, and other options include fluoroquinolones, rifampin, and trimethoprim/sulfamethoxazole; combination therapy is frequently used for neuroretinitis, and IV gentamicin is given for 2 weeks if there is endocarditis. Prolonged therapy (eg, weeks to months) is usually necessary. In vitro antibiotic susceptibilities often do not correlate with clinical results.