Cat-Scratch Disease

Key Features

Essentials of Diagnosis

• 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)

General Considerations

• 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

Demographics

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

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

Clinical Findings

Symptoms and Signs

• 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)

Differential Diagnosis

• Pyogenic adenitis

• Tuberculosis (typical and atypical)

• Tularemia

• Plague

• Brucellosis

• Lymphoma

• Primary toxoplasmosis

• Infectious mononucleosis

• Lymphogranuloma venereum

• Fungal infections

Diagnosis

• 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 ...