Cat Scratch Disease (Bartonella Henselae Infection) - Diagnosis

Differential Diagnosis

• All causes of lymphadenopathy

• Infection

1. Pyogenic lymphadenitis
2. Cervical adenitis caused by mycobacteria
3. Tularemia
4. Toxoplasmosis
5. Plague
6. Fungal disease
7. Viral illness (e.g., HIV, Epstein–Barr virus, cytomegalovirus)
8. Syphilis
9. Others

• Benign or malignant neoplasms

1. Lymphoma may mimic disseminated CSD.

• Other

1. Cysts
2. Sarcoidosis
3. Kawasaki syndrome

• Skin lesion with regional lymphadenopathy

1. Nocardiosis
2. Atypical mycobacteria
3. Tularemia
4. Leishmaniasis
5. Sporotrichosis

• CSD should be suspected if a patient:

1. Has a history of exposure to cats
2. Develops lymphadenopathy and a skin lesion

• Diagnosis is mainly clinical.
• Supportive testing options

1. Specific serologic tests produce positive results in 70–90% of patients with intact immunity but may display cross-reactivity.
2. Biopsy findings may be helpful.
3. Cultures (blood, tissue) are rarely positive.
4. Polymerase chain reaction is used mostly in research settings.

• The serum immunofluorescent antibody test for B. henselae is problematic.

1. Cross-reactivity for B. henselae and B. quintana
2. Significant false-positive rates, but in general:

• Titers < 1:64 suggest that the patient does not have a current Bartonella infection but may indicate past infection.
• Titers of 1:64–1:256 suggest possible Bartonella infection; repeat testing in 10–14 days is recommended.
• Titers > 1:256 strongly suggest active or recent infection.
• Sensitivity is ~85%; specificity is ~95%.
• Tissue histopathology with Warthin–Starry silver stain may show bacilli in clusters.

• Cultures are rarely positive; the organism is fastidious and slow-growing.

1. Colonies may grow after prolonged incubation (1–4 weeks) on specialized media.

• Polymerase chain reaction is under development.

• Not indicated
• Neurologic involvement is usually associated with normal CT of the head.
• Abdominal imaging may show hepatosplenomegaly.

• Biopsy

1. Warthin–Starry silver staining
2. The histopathologic hallmark of CSD is granulomatous inflammation with stellate necrosis but no evidence of angiogenesis.

• Lumbar puncture in patients with neurologic disease may show mild mononuclear pleocytosis.