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Detailed information of CAT SCRATCH DISEASE
CAT SCRATCH DISEASE
DEFINITION:
A benign, self-limited regional lymphadenitis characterized by a
tender regional lymphadenopathy lasting up to 3 weeks.
EPIDEMIOLOGY:
- incidence: 6.6/100,000
- age of onset:
- less than 21 years of age in 80-90% of cases
- risk factors:
- exposure to cats (see below)
- seasonal - 75% of cases occur between September -> March
- M > F (3:2)
PATHOGENESIS:
- association of lymphadenitis with cat scratches first
described by Robert Debre in 1931
- route of transmission:
- 90% of patients give a history of being exposed to a cat
- 75% of these have experienced a cat scratch or bite
- kittens with fleas or kittens 12 months old or younger
pose the greatest risk
- may also become infected if a skin abrasion has been
licked by an infected cat or through conjunctival inoculation
site - inoculation site found in 65% of patients
- cats which transmit the infection show no evidence of in-fection
- dogs have been implicated in about 5% of cases
2. Pathogenesis
- cat scratch -> inoculation at site of scratch -> lesion (macule,
papule and/or vesicle) forms between 3-10 days after inoculation
(and can last from several days to months) -> regional tender,
painful adenopathy within 1-2 weeks after inoculation (with
striking erythema of the overlying skin)
- close contact with a cat -> conjunctival inoculation with
the pathogens -> regional lymphadenitis
- the primary pathogen appears to be Rochalimaea henselae (a
rickettsia) but may also be Afipia felis (a gram-negative
bacil-lus)
- more than 80% of the infected lymph nodes are found on the
head, neck, arms, and axillae
- lymph node involvement:
CLINICAL FEATURES:
- chronic tender lymphadenopathy only (49%)
- fever (38-41 C) - usually lasts 1-7 days (32%)
- malaise/fatigue (30%)
- anorexia, emesis, weight loss (15%)
- headache (14%)
- splenomegaly (11%)
- pharyngitis (8%)
- transient truncal maculopapular rash (5%)
2. Atypical Features
- inoculation site
- painless but little or no conjunctival discharge
- swelling and discolouration may be impressive
2. Adenopathy
- usually preauricular but can include submandibular or
anterior cervical
- syndrome resolves spontaneously within 2-4 months
without any residual complications
2. Neurological Manifestations
- usually accompanied by a fever and occur 1-6 weeks after
the adenopathy begins
- facial nerve paresis
- myelitis
- neuroretinitis
- polyneuritis
- radiculitis
3. Others
- thrombocytopenic purpura
- osteitis
- hepatomegaly/hepatosplenomegaly with hepatic granulomata
INVESTIGATIONS:
- lymphoid hyperplasia, abscesses, granulomas
2. Screening/Confirming Tests
- to detect antibodies to R. henselae
- positive predictive value of 91%
2. Skin Test
- positive in 90% of patients
- there is a false-positive and false-negative rate
- there is a lack of standardized CSD antigen preparation
3. Others
- esosinophila, minimal leukocytosis with left shift
- elevated ESR in first 2 weeks
2. Cerebral Spinal Fluid
- usually normal but may show minimal pleocytosis or
elevated protein
3. EEG
- may be abnormal in those with encephalopathy but return to
normal after several months
MANAGEMENT:
- antipyretics, analgesics
- local heat to involved lymph nodes
- aspiration may relieve pain if suppurated
- avoid incision and drainage for may leave scar and draining
fistula
- antibiotics is not indicated in most cases (gentamicin has
been used in some severe cases)
- disposal of cat is not recommended as they carry the
bacillus for only a short period of time
2. Prognosis
- self-limiting benign disorder (except in those with AIDS)
- those with CNS involvement will recover completely within 1
year without any neurologic sequelae
3. Reference
- Pediatrics in Review 15(9): 348-353 (1994)
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Pediatric Database - CAT SCRATCH DISEASE
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