Cat Scratch Disease



Cat Scratch Disease


Roberto N. Miranda, MD





Key Facts


Terminology



  • Necrotizing inflammation caused by Bartonella henselae


Etiology/Pathogenesis



  • Bartonella henselae causes most cases of CSD


  • 90% of patients report contact with cats


  • B. henselae causes CSD in mostly immunocompetent patients


  • B. henselae in immunocompromised patients can cause bacillary angiomatosis


Clinical Issues



  • Primary lesion in skin appears as 0.5-1 cm erythematous papule at site of cat scratch


  • Regional lymphadenopathy appears 1-3 weeks after inoculation


  • In immunocompetent patients, disease is self-limited and confined to lymph nodes


Microscopic Pathology



  • Follicular lymphoid hyperplasia with prominent germinal centers


  • Early lesions show eosinophilic necrosis admixed with neutrophils in subcapsular sinus


  • Advanced changes show stellate necrotizing microabscesses and granulomas


Ancillary Tests



  • Bacteria are more easily identified by immunohistochemistry than by Warthin-Starry stain


  • Serology is considered practical method for diagnosis, but it has shortcomings







Lymph node in a patient with an early lesion of cat scratch disease (CSD) shows follicular hyperplasia image and a small interfollicular area of necrosis image.






Advanced lesion of CSD shows stellate granulomas image with central necrosis image. Bacteria are less likely to be identified at this stage. Hyperplastic follicles image are also present.


TERMINOLOGY


Abbreviations



  • Cat scratch disease (CSD)


Synonyms



  • Parinaud oculoglandular syndrome


Definitions



  • Necrotizing inflammation caused by Bartonella henselae


ETIOLOGY/PATHOGENESIS


Infectious Agents



  • Bartonella henselae causes most cases of CSD



    • B. quintana causes a minority of CSD cases


    • Patients with CSD are usually immunocompetent


  • Bartonella henselae is name adopted since 1993



    • Earlier names were Afipia felis and Rochalimaea henselae


    • Bacteria are small, pleomorphic, curved, motile, Gram-negative bacilli, oxidase-negative


    • Culture is difficult; bacteria can take 2-6 weeks to grow



      • Better yield in systemic disease; poor yield from lymph node


  • Patients report contact with cats in 90% of cases



    • Approximately 60% of patients report antecedent cat scratch


  • Bacilli are transmitted to humans through bite or scratch of infested cat


  • Healthy cats with fleas are reservoir for B. henselae



    • B. henselae resides in erythrocytes of cats and does not cause illness



      • B. henselae has also been isolated from fleas of cats carrying bacilli


  • Granuloma formation results from activation and accumulation of histiocytes



    • Thought to be secondary to interferon-γ-mediated TH1 cell response


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Bartonella henselae has worldwide distribution


    • Approximately 22,000 cases of CSD are diagnosed each year in United States



      • CSD is most frequent cause of benign lymphadenopathy in children and young adults


    • Seasonal distribution; most cases occur between July and January


    • Relative incidence of CSD in adults is increasing; currently approximately 40%


Presentation



  • Spectrum of disease ranges from localized to systemic



    • Most patients have mild disease with malaise, generalized aching; about 2/3 of patients have fever


  • Primary lesion in skin appears as 0.5-1 cm erythematous papule



    • At site of cat scratch


    • Skin lesion appears 3-10 days after inoculation


    • Initial papular lesion is followed by vesicle that oozes fluid and eventually dries


  • Upper extremities are more frequently affected, followed by cervical and facial regions


  • Regional lymphadenopathy appears 1-3 weeks after inoculation



    • Lymphadenopathy is tender with erythematous overlying skin



      • Suppuration occurs in approximately 10% of cases


    • Lymphadenopathy is localized or regional in 85% of patients, but it can affect multiple areas


  • Parinaud syndrome consists of conjunctivitis and preauricular lymphadenopathy




    • Conjunctiva shows ulceration, chronic inflammation, and necrotic granulomas


Laboratory Tests



  • Minimal leukocytosis with or without eosinophilia can occur


  • Bacteria can be isolated and cultured from clinical specimens


  • Intradermal skin test is obsolete because lack of standardization and risk of transmissible diseases



    • Test required use of aspirated suppurative material from clinical specimens


Natural History



  • In immunocompetent patients, CSD is self-limited and confined to lymph nodes



    • Usually lasts 2-4 months if no therapy is administered


    • 1-2% of patients may have prolonged fever, suppurative lymphadenitis, or systemic symptoms


  • In immunocompromised patients, disease may become systemic, severe, and life-threatening



    • Multiorgan involvement in this subset of patients


Treatment



  • Varies depending upon clinical presentation and immune status of patient



    • CSD usually does not respond to therapy


    • Several studies could not demonstrate that antibiotic therapy changes course of disease



      • No decrease in duration of disease or probability of suppuration


Prognosis



  • CSD is self-limited disease with excellent prognosis


MACROSCOPIC FEATURES


General Features



  • Lymph nodes are enlarged, matted, and adherent to surrounding soft tissues or skin


  • Focal areas of necrosis or microabscesses are grossly visible


MICROSCOPIC PATHOLOGY


Histologic Features



  • Early lesions in lymph nodes



    • Follicular lymphoid hyperplasia with germinal centers showing abundant tingible body macrophages


    • Eosinophilic necrosis admixed with neutrophils or karyorrhexis in subcapsular sinus



      • Tends to extend into adjacent germinal centers


    • Patches of monocytoid cells within sinuses are also noted


    • Dilated sinuses contain lymphocytes, histiocytes, and immunoblasts


  • Progressive changes in lymph nodes



    • Small abscesses with necrosis and clusters of neutrophils



      • Initially in subcapsular sinus; subsequently in cortex and then medulla


  • Advanced changes in lymph nodes



    • Classic stellate necrotizing granulomas of CSD


    • Macrophages surround abscess-forming rim of epithelioid cells



      • Epithelioid cells include rare multinucleated, Langhans-type cells


  • Warthin-Starry silver impregnation stain is useful to visualize bacteria



    • Chances of visualizing bacteria in lymph nodes is highest in early lesions


  • Skin lesions



    • Rarely biopsied


    • Histologic features similar to those described in lymph nodes



ANCILLARY TESTS


Histochemistry

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Cat Scratch Disease

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