Cat scratch disease is usually a
self-limited infection by a curved pleomorphic gram-negative, bacteria
Bartonella
henselae.
Visit:Bartonellosis
;
verruga
peruana ;
bacillary angiomatosis.
The bacteria form filaments up to 10
micrometer or longer.
It is
easily seen in tissue sections of the skin, lymph nodes, and
conjunctiva, when stained by a silver impregnation technique.
Cats are the
principal reservoir of Bartonella henselae, the etiologic agent in
most cases of CSD.
Infection begins when the organism is inoculated into the skin by the
claws of cats and rarely by other animals, or by thorns or splinters.
Sometimes the conjunctiva is
contaminated by close contact with a cat, possibly by licking around
the eye.
Infections are more common in children
(80%) than in adults, and there may be clustering when a stray cat or
kitten joins a family.
Most patients have a papule at the site
of inoculation, but it may be small and overlooked.
The papule, which begins 3 to 14 days
after inoculation may persist for 8 weeks, is followed by tenderness
and enlargement of the regional lymph nodes.
The nodes remain enlarged for 3 to 4
months and may drain through the skin. About one-half of the patients
have other symptoms, including fever and malaise and (rarely)
splenomegaly, Parinaud’s oculoglandular syndrome, rash encephalitis
(which typically has a sudden onset and sudden resolution), and
erythema nodosum.
Rare complications of B.
henselae infection is
bacillary angiomatosis.
At the site of inoculation the bacteria
multiply in the wall of the small vessels and about collagen fibers
from which they move through draining lymphatics to regional
lymphnodes, where they produce a pyogranulomatous lymphadenitis.
In early lesions clusters of bacteria
expand and obliterate the walls of small vessels.
The lesions in the skin and lymphnodes
progress from abscesses to suppurating granulomas and finally to
necrosis.
Image1 ;
Image2
Bacteria are abundant in early lesions
and rare in late ones.
Without biopsy and the visualization of
the characteristic bacteria, the diagnosis is supported when three
criteria are met : i) contact with a cat, a cat scratch, or a primary
lesion of the skin or conjunctiva : ii)a positive skin test for cat
scratch antigen : ii)and negative results from laboratory studies for
other causes of lymphadenopathy.
Although
serologic testing is the reference method for diagnosis, successful
use of immunohistochemical (IHC) stain of regional lymph nodes for the
diagnosis of CSD has been reported.
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