Cat Scratch Disease



Cat Scratch Disease


Irina Margaritescu, MD, DipRCPath

Bruce R. Smoller, MD





Key Facts


Etiology/Pathogenesis



  • Domestic cats represent natural reservoir and vectors


  • Cat scratch disease (CSD) is caused by Bartonella henselae (B. henselae), and bacillary angiomatosis (BA) is caused by both B. henselae and Bartonella quintana


Clinical Issues



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


  • Papules or pustules appear at inoculation site in 3-12 days


  • Regional lymphadenopathy usually occurs after 10-30 days


  • Immunocompromised patients develop bacillary angiomatosis, bacillary peliosis, or relapsing fever with bacteriemia


Microscopic Pathology



  • Cutaneous lesions of CSD show zone of necrosis, fibrin, neutrophils, and nuclear debris in dermis surrounded by mantle of macrophages, lymphocytes, and plasma cells


  • Cutaneous lesions of BA are characterized by vascular proliferation in lobular pattern


  • Accompanied by lymphocytes, histiocytes, neutrophils, and nuclear dust of neutrophils and clumps of granular purplish material (masses of bacteria) in immediate vicinity of some vessels


Ancillary Tests



  • Organisms demonstrated by Warthin-Starry stain and immunohistochemistry






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



Abbreviations



  • Cat scratch disease (CSD)


Synonyms



  • CSD: Cat scratch fever, regional granulomatous lymphadenitis


  • Bacillary angiomatosis (BA): Epithelioid angiomatosis



Definitions



  • CSD: Self-limiting infectious disease characterized by subacute, regional lymphadenitis, usually following scratch or bite of cat


  • BA: Infectious disease that appears in immunocompromised patients following scratch or bite of cat, characterized by vasoproliferative lesions usually, but not exclusively, seen in skin


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



Treatment



  • Options, risks, complications



    • Most cases of CSD require only supportive and symptomatic care


    • Management of mild to moderate infections in immunocompetent patients consists of reassurance, adequate follow-up, and analgesics for pain


    • Antibiotic treatment (azithromycin, erythromycin, doxycycline, or gentamicin) is necessary for severe infections, particularly when lymph nodes are severely affected and when organs other than lymph nodes have become involved


    • Immunocompromised patients tend to develop more severe Bartonella infections and may require prolonged antibiotic treatment


    • Avoidance of unnecessary manipulation, including incision and drainage of lymph nodes, is advisable as this may leave scars without hastening recovery


  • Surgical approaches



    • Occasionally, lymph node aspiration is indicated for symptomatic relief of tender, fluctuant nodes


    • Excision of lymph nodes is not justified therapeutically although it may occasionally be indicated for histology


Prognosis

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

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