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Key Features

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Essentials of Diagnosis
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  • History of a cat scratch or cat contact

  • Primary lesion (papule, pustule, or conjunctivitis) at site of inoculation

  • Acute or subacute regional lymphadenopathy

  • Laboratory studies excluding other causes

  • Biopsy of node or papule showing histopathologic findings consistent with cat-scratch disease and occasionally characteristic bacilli on Warthin-Starry stain

  • Positive cat-scratch serology (antibody to Bartonella henselae)

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General Considerations
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  • Usually a benign, self-limited form of lymphadenitis

  • Patients often report a cat scratch (67%), bite (less common), or contact with a cat or kitten (90%)

  • Cats become infected via an infected flea; the flea becomes infected when feeding on a cat that is bacteremic with B henselae

  • Occasionally dogs can be infected and transmit disease disease

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Demographics
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  • Occurs worldwide and is more common in the fall and winter

  • More than 20,000 cases occur per year in the United States

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Clinical Findings

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Symptoms and Signs
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  • Primary lesion develops at the site of the wound in about 50% of patients

    • Lesion usually is a papule or pustule that appears 7–10 days after injury

    • Located most often on the arm or hand (50%), head or leg (30%), or trunk or neck (10%)

    • May be conjunctival (10%)

  • Regional lymphadenopathy

    • Appears 10–50 days later

    • May be accompanied by mild malaise, lassitude, headache, and fever

    • Multiple sites are seen in about 10% of cases

    • Involved nodes may be hard or soft and 1–6 cm in diameter; they are usually tender, warm, and erythematous and 10–20% suppurate

    • Lymphadenopathy usually resolves in about 2 months but may persist for up to 8 months.

  • Unusual manifestations include

    • Erythema nodosum

    • Thrombocytopenic purpura

    • Conjunctivitis (Parinaud oculoglandular fever)

    • Parotid swelling

    • Pneumonia

    • Osteolytic lesions

    • Mesenteric and mediastinal adenitis

    • Neuroretinitis

    • Peripheral neuritis

    • Hepatitis, granulomata of the liver and spleen

    • Encephalopathy

  • Immunocompetent patients

    • Have prolonged fever, fatigue, and malaise

    • Lymphadenopathy may be present

    • Hepatosplenomegaly or low-density hepatic or splenic lesions visualized by ultrasound or CT scan are seen in some patients

  • Immunocompromised patients

    • Infection may take the form of bacillary angiomatosis, presenting as vascular tumors of the skin and subcutaneous tissues

    • May have bacteremia or infection of the liver (peliosis hepatis)

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Differential Diagnosis
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  • Pyogenic adenitis

  • Tuberculosis (typical and atypical)

  • Tularemia

  • Plague

  • Brucellosis

  • Lymphoma

  • Primary toxoplasmosis

  • Infectious mononucleosis

  • Lymphogranuloma venereum

  • Fungal infections

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Diagnosis

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  • Serologic evidence of Bartonella infection by indirect immunofluorescent antibody with IgG titer of > 1:256 is strongly suggestive of recent infection

  • A positive IgM antibody is sometimes positive

  • Polymerase chain reaction assays are available

  • Cat-scratch skin test antigens are not recommended

  • Histopathologic examination of involved tissue may show

    • Pyogenic granulomas

    • Bacillary forms demonstrated by Warthin-Starry silver stain (bacillary forms on stain are not specific for cat scratch disease)

  • Necrotizing granulomas may be seen

  • Erythrocyte sedimentation rate is usually elevated

  • In patients with ...

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