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A benign,
self-limited regional lymphadenitis characterized by a tender regional
lymphadenopathy lasting up to 3 weeks.
Incidence is
6.6/100,000, with an age of onset of less than 21 years of age in 80-90%
of cases. Risk factors include exposure to cats (see below), seasonal
variation - 75% of cases occur between September - March, and a M > F
(3:2) preponderance.
Robert Debre
first described the association of lymphadenitis with cat scratches in
1931. Ninety percent of patients give a history of being exposed to a
cat , with 75% of these having experienced a cat scratch or bite.
Kittens with fleas or kittens 12 months old or younger pose the greatest
risk, but infection may also occur if a skin abrasion has been licked by
an infected cat or through a conjunctival inoculation (found in 65% of
patients). Cats, which transmit the infection, show no evidence of
infection, and dogs have been implicated in about 5% of cases.
A cat scratch
causes an inoculation at the site of the scratch. A ;esion (macule,
papule and/or vesicle) forms between 3-10 days after inoculation (and
can last from several days to months). There is regional tender, painful
adenopathy within 1-2 weeks after inoculation (with striking erythema of
the overlying skin). The primary pathogen appears to be Rochalimaea
henselae (a rickettsia) but may also be Afipia felis (a gram-negative
bacillus). More than 80% of the infected lymph nodes are found on the
head, neck, arms, and axillae. Lymph node involvement is primarily a
single node (50%). In 80% of cases, the lymphadenopathy ranges from 1-5
cm. Lymphadenopathy usually regresses over 2-6 months but can persist
for as long as 2 years (suppuration is seen in about 10% of cases but
cellulitis is rare).
Clinical
features are as follows:
1.
Typical Features (80-95% of cases)
a.
Chronic tender lymphadenopathy only (49%)
b.
Fever (38-41 C) - usually lasts 1-7 days (32%)
c.
Malaise/fatigue (30%)
d.
Anorexia, emesis, weight loss (15%)
e.
Headache (14%)
f.
Splenomegaly (11%)
g.
Pharyngitis (8%)
h.
Transient truncal maculopapular rash (5%)
2.
Atypical features
a.
Parinaud Oculoglandular Syndrome (2-17%)
i. Conjunctival Granuloma
1. Inoculation site
2. Painless but little or no
conjunctival discharge
3. Swelling and discolouration may be
impressive
4.
b.
Adenopathy
1. Usually preauricular but can include
submandibular or anterior cervical
2. Syndrome resolves spontaneously within 2-4
months without any residual complications
Neurological
complications are usually accompanied by a fever and occur 1-6 weeks
after the adenopathy begins. These can include
encephalopathy/encephalitis, seizures (focal or generalized), severe,
combative behaviour, extreme lethargy or coma and/or cranial /peripheral
nerve involvement (facial nerve paresis, myelitis, neuroretinitis,
polyneuritis, and radiculitis.
Other
complications include thrombocytopenic purpura, osteitis, and
hepatomegaly/hepatosplenomegaly with hepatic granulomata.
Investigations
may include a lymph node biopsy (lymphoid hyperplasia, abscesses, and
granulomas), serology (to detect antibodies to R. henselae), and skin
testing (positive in 90% of patients). Other studies include serum
studies (esosinophila, minimal leukocytosis with left shift , and an
elevated ESR in first 2 weeks), cerebral spinal fluid (normal but may
show minimal pleocytosis or elevated protein), and an EEG which may be
abnormal in those with encephalopathy, but return to normal after
several months.
Management is
primarily supportive:
a.
Antipyretics, analgesics
b.
Local heat to involved lymph nodes
c.
Aspiration may relieve pain if suppurated
d.
Avoid incision and drainage for may leave scar and draining
fistula
e.
Antibiotics is not indicated in most cases (gentamicin has been
used in some severe cases)
f.
Disposal of cat is not recommended as they carry the bacillus
for only a short period of time
Prognosis is
good as it is a self-limiting benign disorder (except in those with
AIDS). Those with CNS involvement will recover completely within 1 year
without any neurologic sequelae
This edited version is
being used with the permission of its original author, Dr.
Alan Gandy.
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