Bacillary Angiomatosis



Bacillary Angiomatosis


Roberto N. Miranda, MD





Key Facts


Terminology



  • Nodules of small blood vessels resulting from infection by bacterium Bartonella henselae


Etiology/Pathogenesis



  • B. henselae and B. quintana are most common agents isolated from BA


  • Domestic cats are major reservoir for B. henselae; transmitted by fleas from cat to cat


Clinical Issues



  • Most affected patients are immunosuppressed (e.g., AIDS)


  • Cutaneous lesions can be 1 or many (up to hundreds)



    • Red to violaceous, dome-shaped papules and nodules


  • Lymphadenopathy may be regional or localized to area of trauma


  • Bacteria can be cultured from clinical specimens such as blood, tissues, or cytologic specimens


Microscopic Pathology



  • Blood vessels can show spectrum of differentiation


  • Interstitium shows edema, scattered spindle cells, neutrophils, or foamy histiocytes


Ancillary Tests



  • Warthin-Starry or Giemsa stain can highlight organisms


  • Monoclonal antibodies specific for B. henselae can identify bacterial organisms


  • PCR is helpful to identify organism







Lymph node with bacillary angiomatosis. A pale vascular nodule image dissecting lymphoid tissue image is seen.






This vascular nodule shows numerous small vessels containing red cells image, surrounded by an edematous stroma image.


TERMINOLOGY


Abbreviations



  • Bacillary angiomatosis (BA)


Synonyms



  • Epithelioid angiomatosis


Definitions



  • Nodules of small blood vessels resulting from infection by bacterium Bartonella henselae


ETIOLOGY/PATHOGENESIS


Infectious Agents



  • Bartonella henselae is most common agent isolated from BA



    • Small, curved, motile, Gram-negative bacilli, oxidase-negative


    • Culture is difficult, and bacteria may take 2-6 weeks to grow



      • Growth requires CO2 rich environment and enriched media


      • Better yield in patients with systemic disease; poor yield from tissues


      • Isolates may be obtained in 40% of cases of BA and 6% of cases with cat scratch disease


  • Bartonella quintana, the agent of trench fever, also can cause BA


  • Bartonella enters endothelial cells by endocytosis



    • Gives rise to Bartonella-containing vacuoles or by invasome-mediated internalization


    • Invasome involves formation of cell surfaceassociated bacterial aggregates, which are engulfed


  • Bartonella effector protein A BepA and VirB/VirD4 type IV secretion system are associated with vascular sprout formation


  • Bartonella henselae is name adopted since 1993



    • Earlier name: Rochalimaea henselae


Susceptibility



  • B. henselae infections in patients with HIV infection can manifest as BA



    • HIV(+) homosexual patients, intravenous drug users, and transfusion recipients are at risk


    • Rarely, patients with other types of immunosuppression can develop BA


  • B. henselae infections in immunocompetent patients can result in cat scratch disease


Pathogenesis



  • Domestic cats are major reservoir for B. henselae



    • Transmitted by cat fleas from cat to cat


    • Up to 1/2 of domestic cats carry anti-Bartonella henselae antibodies


  • B. henselae causes bacteremia in cats; organism colonizes erythrocytes


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


  • B. quintana is unusual cause of BA



    • B. quintana is more frequently associated with “urban trench fever”



      • Trench fever is characterized by recurrent and cycling fevers, malaise, bone pain, and splenomegaly


      • Homeless persons exposed to human louse (Pediculus humanus corporis) are more susceptible to B. quintana


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Most affected patients are immunosuppressed as result of HIV infection



      • BA is uncommon but can occur in patients with other types of immunosuppression


      • Very rare cases of BA occur in immunocompetent persons



    • Many patients are men; 31-56 years of age



      • In large part, this correlates with high percentage of HIV(+) men


Presentation



  • Although cats are major reservoir, history of cat exposure is a variable



    • It is common for affected patients to not have history of contact with cats


  • Cutaneous BA may show concomitant involvement of other sites



    • Mucous membranes, lymph nodes, soft tissues, spleen, liver, and bones


  • Cutaneous lesions: Single up to many (hundreds), red to violaceous, dome-shaped papules and nodules



    • Trunk and extremities are preferentially affected


  • Lymph node involvement is more frequently associated with B. henselae than with B. quintana



    • Lymphadenopathy may be regional or localized to area of trauma


  • Extracutaneous involvement can occur in absence of concurrent skin lesions


Laboratory Tests



  • No specific hematologic changes


  • Bacteria can be cultured from clinical specimens such as blood, tissues, or cytologic specimens


Treatment



  • Patients with BA can benefit from erythromycin or doxycycline


  • Hepatosplenic disease may benefit from trimethoprimsulfamethoxazole, gentamicin, ciprofloxacin, and rifampin


Prognosis



  • Most skin lesions resolve spontaneously


  • Early diagnosis of various affected organs leads to cure


  • Unrecognized progressive disease can be fatal


MICROSCOPIC PATHOLOGY


Histologic Features



  • Lymph nodes involved by BA typically drain skin lesions



    • Nodules composed of blood vessels of variable size and shape



      • Vascular nodules can become confluent and form large masses


    • Blood vessels show a spectrum of differentiation



      • Round, large, irregular, or ectatic to small solid clusters with barely visible lumina


    • Endothelial nuclei are prominent, with single or multiple small nucleoli



      • Usually no multilayering of endothelial cells lining vessels


    • Mitotic figures are present; up to 3-5 per high-power field


    • Blood vessels can be surrounded by deeply eosinophilic interstitial material



      • Corresponds to bacterial aggregates


    • Interstitium may show loculated edema, scattered spindle cells, and inflammatory cells


  • Skin



    • Skin lesions can affect upper or deep dermis and subcutis


    • Lobules of newly formed blood vessels



      • Cytologically similar to those in lymph node


    • Overlying epidermis may be thin


  • Peliosis hepatis &/or peliosis splenis can occur



    • Cystic, blood-filled spaces in liver and spleen; can occur in immunocompromised patients


ANCILLARY TESTS


Histochemistry



  • Warthin-Starry (WS) stain highlights bacteria that appear as clumps of rods or as individual small rods



    • Bacteria can be found within endothelial cells or in macrophages




      • WS stain is technically difficult; skill is required to avoid precipitate that mimics bacterial organisms


      • Interpretation of good quality stain can be time consuming


    • Clusters of bacteria appear around blood vessels



      • Correspond to perivascular eosinophilic deposition seen on H&E stain


  • Giemsa stain may also highlight bacteria; appear violaceous


Immunohistochemistry



  • FVIIIRAg(+), ULEX-1(+)



    • Highlight endothelial cells


    • Reactivity correlates with degree of differentiation


  • CD31(+), CD34(+) in most cases


  • Monoclonal anti-B. henselae antibody reacts in fixed paraffin-embedded tissue; can confirm presence of bacteria


PCR

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Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Bacillary Angiomatosis

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