Cat Scratch Disease



Cat Scratch Disease


Irina Margaritescu, MD, DipRCPath

Bruce R. Smoller, MD









Clinical photograph shows regional submandibular lymphadenopathy image in a case of cat scratch disease. (Courtesy L. Thompson, MD.)






H&E demonstrates the microscopic features of cat scratch disease lymphadenitis, showing hyperplastic follicles image and stellate necrotizing granulomas image.


TERMINOLOGY



Synonyms



  • CSD: Cat scratch fever, regional granulomatous lymphadenitis


  • Bacillary angiomatosis (BA): Epithelioid angiomatosis



ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Natural reservoir and vectors are domestic cats, especially kittens and stray cats


  • Occasional cases of CSD associated with dog and monkey bites have been reported


Infectious Agents



  • Bartonella henselae (formerly Rochalimaea henselae)



    • Causative agent of CSD, BA, and endocarditis


    • Small, pleomorphic, intracellular, slow-growing, weakly gram-negative bacillus


    • Houston-1 and Marseille (genotype II) identified as main genogroups


  • Bartonella quintana



    • Causative agent of both trench fever and BA


    • Less frequently associated with BA than B. henselae


  • Bartonella clarridgeiae rarely associated with CSD cases


Pathogenesis



  • Only genus that infects human erythrocytes and triggers pathological angiogenesis in vascular bed


  • Highly adapted pathogens that infect and persist in erythrocytes and endothelial cells of host circulatory system through various mechanisms



    • Induction of pathological angiogenesis, with concomitant production of pseudoneoplastic lesions in human vasculature (i.e., BA and bacillary peliosis)


    • Use of adhesins for endothelial cells


    • Incorporation of lipopolysaccharides with low endotoxic potency in outer membrane (antagonistic to host’s innate immune response)


  • Colonization of secondary foci at considerable distances from primary site of infection, with preference for highly vascularized tissues like heart valves, liver and spleen, or cooler areas of body, such as vascular beds of skin


  • Response to infection depending on immune status of infected host



    • Granulomatous and suppurative response in immunocompetent individuals


    • Vasoproliferative response in immunocompromised persons


CLINICAL ISSUES


Epidemiology



  • Incidence



    • At least 9.3 per 100,000 population for CSD


    • Greater in regions with higher temperature and humidity


    • Incidence peaks in fall and winter months


  • Age



    • CSD affects persons in all age groups, but most are < 21 years (60-80%)


    • BA affects children very rarely


  • Gender



    • CSD and BA more common in males



Presentation



  • History of recent exposure to cats (scratch, bite, lick)


  • 1 or more cutaneous papules or pustules may appear at inoculation site in 3-12 days


  • Regional lymphadenopathy (most remarkable manifestation) usually occurs after 10-30 days



    • Cervical, axillary, or epitrochlear nodes typically involved


  • Usually mild constitutional symptoms including malaise, anorexia, nausea, fatigue, headache, and low-grade fever


  • Atypical presentation in up to 10% of cases



    • Encephalopathy, neuroretinitis, prolonged fever, arthritis, synovitis, atypical pneumonitis, and endocarditis


    • Granulomatous conjunctivitis and ipsilateral preauricular lymphadenitis (Parinaud oculoglandular syndrome) caused by conjunctival inoculation


  • Visceral involvement with hepatitis/splenitis


  • Skin manifestation including nonspecific rashes, erythema nodosum, and leukocytoclastic vasculitis


  • Immunocompromised patients may develop BA, bacillary peliosis, or persistent or relapsing fever with bacteremia



    • BA



      • Vasculoproliferative disease that primarily involves skin but can involve other organs


      • Numerous brown to violaceous tumors of skin and subcutaneous tissues


      • Lesions very similar to verruga peruana, the chronic form of Carrión disease (Oroya fever)


Laboratory Tests



  • Diagnosis of both CSD and BA strongly suggested by history and physical findings


  • Laboratory findings



    • Occasionally, mildly elevated white blood cell count, elevated or diminished platelet count, and elevated erythrocyte sedimentation rate in CSD


    • Anemia, leukopenia, CD4(+) cell count < 200/µL in patients with BA and HIV



Prognosis

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