Rapid Revision: Cat Scratch Disease

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This is the first post on the blog which I am posting via the Windows Live Writer. There may be some bits and bobbles which are out of place or not in sync with the rest of the posts owing to that. I will modify all of them post-publication. WL seems like a very cool tool especially for me, since I do a lot of my blog writing offline anyways. And the image handling promises to be easy to maintain. So, let’s see how this goes!



  • Causative agent: Bartonella henselae
  • Almost global distribution
  • Cats are the primary hosts which transmit the disease via bites, licks or scratching.
  • Asymptomatic bacteremia is high in kittens
  • Ctenocephalus felis, the cat flea, is also a vector for dissemination between animals

ctenocephalus felis

Clinical Presentation:

Primary Inoculating Lesion:

  • 0.5-1 cm papule, vesicle or nodule that appears at the site of introduction and persists for 1-3 weeks. Often missed.


ax ln ped.wisc

  • Develops within 2-3 weeks (range: 3 – 50 days) after the inoculation
  • Unilateral solitary or regional lymphadenopathy corresponding to the site of the lesion.
  • Nodes are tender, firm, mobile, with erythema of the overlying skin.
  • About 10% nodes suppurate
  • Usually resolves within 3 months

Non-Specific Systemic Symptoms:

  • Fever
  • Anorexia
  • Myalgia
  • Malaise
  • Headache
  • Abdominal pain

Atypical Presentations:

Perinaud’s Oculoglandular Syndrome:


  • Frequently reported atypical presentation seen following inoculation into conjunctiva or eyelids
  • Unilateral manifestations are common, showing:
    • Conjunctivitis
    • Granulomatous lesions
    • Presuricular Lymphadenopathy

Disseminated Disease:

  • Systemic spread may occur independent of the typical presentation
  • Involves most commonly:
    • Nervous system
    • Viscera
    • Bones
  • May cause neuroretinitis with sudden painless loss of vision. Most ocular complications resolve without any residual damage over a period of several months.
  • Rarer complications:
    • Encephalitis
    • Peripheral neuropathy/neuritis
    • Myelitis
    • Facial palsy
    • Granulomatous hepatitis
    • Splenitis


Lymph Nodes:

  • Early in the course:

    • Follicular hyperplasia
    • Arteriolar proliferation
  • Within weeks:

    • Cortical granulomas
    • Occasional multinucleated giant cell
    • Neutrophilic infiltrates
    • Coalescing micro abscesses – stellate micro abscess
    • Granulomas are surrounded by histiocytes and peripheral lymphocytes
  • Warthin – Starry Stain:

    • Typical clusters of pleomorphic gram negative organisms within:
      • Areas of necrosis
      • Blood vessel walls
      • Erythrocytes

LymphNode_CatScratch wbpath

Differential Diagnosis:

  1. Lymphoma
  2. Mycobacterial infection
  3. Soft tissue infection caused by MRSA


    • High degree of suspicion + typical presentation + history of exposure to cats = DIAGNOSIS!
    • Serologic test for antibodies against Bartonella henselae has poor sensitivity.
    • Lymph node biopsy/aspiration
    • PCR analysis of tissue sample
    • Culture is rarely positive


  • Since the manifestations are largely the result of an over-enthusiastic response of the immune system, the role of antibiotics in therapy of the immunocompetent host is highly debated.
  • Azithromycin (Day 1: 500 mg PO. Days 2&3: 250 mg PO) is said to expedite the resolution of the lymphadenopathy.
  • Complications warrant antimicrobial therapy:
    • Retinitis:
      • Doxycycline 100 mg bid x 4-6 weeks
      • Rifampicin 300 mg bid x 4-6 weeks
  • Antimicrobial therapy is highly recommended for the immunocompromised host.

Skeptic Oslerphile, Scientist at the Indian Council of Medical Research, National Institute of Cholera and Enteric Diseases. Interests include: Emerging Infections, Public Health, Antimicrobial Resistance, One Health and Zoonoses, Diarrheal Diseases, Medical Education, Medical History, Open Access, Healthcare Social Media and Health2.0. Opinions are my own!


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