Clinical review

Cat scratch disease

Alexander Williams, general practitioner ^a, Christopher D Sheldon, consultant chest physician ^b, Terry Riordan, consultant microbiologist ^c. 

^a St Thomas Health Centre, Exeter EX4 1HJ, ^b Royal Devon and Exeter Hospital, Wonford, Exeter EX2 5DW, ^c Public Health Laboratory, Royal Devon and Exeter Hospital

Correspondence to: A Williams su1838{at}eclipse.co.uk

Unilateral lymphadenopathy of the groin is commonly seen in general practice. We report on a patient with initial features suggestive of sarcoidosis, but who, after careful history taking and further investigation, had cat scratch disease.

	Case report

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A 29 year old woman visited her general practitioner with a painless swelling in the right groin. She was referred to a surgeon, who aspirated the node. The aspirate contained blood and a range of lymphoid cells, suggesting a reactive lymph node. Ultrasonography confirmed numerous large lymph nodes in the right groin. Lymphadenopathy was not present elsewhere. The pelvis appeared normal on ultrasonography. Two hypoechoic lesions were found in the right lobe of the liver posteriorly, and multiple similar lesions were found in the spleen, but no para-aortic lymphadenopathy was seen.

The surgeon took a biopsy specimen of the lymph node. This showed a reactive lymph node with prominent geminal centres and focal areas in keeping with necrotising granulomata. Cultures were Gram negative. Stains for acid fast bacilli and fungi gave negative results, and there was no evidence of caseating necrosis. Sarcoidosis was suspected, and the patient was referred to a chest physician.

She had no symptoms of systemic disease and had a good appetite, steady weight, and no night sweats. She had never smoked but did have several allergies, including eczema and perennial rhinitis. At initial presentation a full blood count gave normal results. The erythrocyte sedimentation rate was increased at 25 mm in the first hour. A liver function test showed increased concentrations of alkaline phosphatase 188 iu/l (normal range 25-75 iu/l), aspartate aminotransferase 177 iu/l (8-39 iu/l), and -glutamyltransferase 164 iu/l (12-43 iu/l). Serum amylase concentrations were 30 iu/l, within normal range (23-71 iu/l). A monospot test for infectious mononucleosis gave a negative result. A test for Epstein-Barr nuclear antigen antibody gave a positive result, indicating past infection with the Epstein-Barr virus. There was no evidence of infection with Mycoplasma pneumoniae, Coxiella burnetii (Q fever), or Chlamydia psittaci (all titres were <10 with the complement fixation test). Serology for Bartonella was performed with an immunofluorescence kit (MRL Diagnostics, Central Public Health Laboratory, London). Although the IgM titre for Bartonella henselae was <20, that for IgG was >256. The IgM titre for Bartonella quintana <20 and for IgG was 1 in 64. These findings were consistent with a recent infection with B henselae.

Computed tomography of the patient's abdomen confirmed enlarged lymph nodes in her right groin. No lymphadenopathy was detected intra-abdominally. Her liver appeared normal both before and after the addition of contrast, but some low density areas were detected in the spleen. Other organs in her upper abdomen appeared normal.

After four months there were still persistently increased titres of IgG to B henselae, and IgM had increased to >20. Interestingly, titres to B quintana also increased, IgG to >128 and IgM to >20. This may represent cross reactivity.

The patient improved over time. She was not given antibiotics, and results of liver function tests returned to normal. At final follow up she recalled that a neighbour's cat had scratched her in the groin about a month before she became unwell.

	Discussion

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Cat scratch disease mainly affects children and young adults (80% of those affected are under 21). Most patients develop regional lymphadenopathy, preceded by an erythematous papule at the site of inoculation. In a survey of 268 patients with cat scratch disease all had lymphadenopathy and other systemic symptoms but less than half had lymphadenopathy alone.¹ Systemic disease is more common in immunocompromised patients and can include fever, malaise, anorexia, headache, and splenomegaly. Complications of systemic infection include pneumonia, encephalitis, and hepatitis.

Members of the genus Bartonella have recently become associated with an increasing spectrum of diseases. Five Bartonella species are associated with diseases in humans, of which B henselae causes the widest spectrum of disease, including diseases with granulomatous features (cat scratch disease), vascular proliferation (bacillary angiomatosis-peliosis), and a combination of bacteraemia and endocarditis.² Bacteraemia may cause lesions of most organs, including the heart, liver, spleen, bone marrow, lymphatics, and central nervous system.³

Another rickettsia-like organism, Bartonella bacilliformis, cause Carrión's disease. This is a biphasic disease limited to parts of the Andes. The acute stage of the disease, Oroya fever, is characterised by severe haemolytic anaemia. The chronic stage, verruga peruana, is manifested by vascular proliferation of the skin. B henselae and B bacilliformis are closely related and have been merged into the genus Bartonella.⁴ B quintana, transmitted by the human body louse, causes trench fever, characterised by fever, rash, bone pain, and splenomegaly. The disease can occur as one episode lasting four or five days. During the first world war over one million troops were estimated to have trench fever.⁵

B henselae is endemic in the United States, Europe, Africa, Australia, and Japan. Cats are the principal reservoir, particularly during the kitten stage, and the main vector to cats is the flea.⁶ Patients with cat scratch disease are likely to own a cat aged 12 months or younger, to have been scratched or bitten by a kitten, and to have at least one kitten infested with fleas.⁷ In a small percentage of patients with cat scratch disease there is no history of contact with animals. ^{8 9}

About 24 000 people have cat scratch disease each year in the United States, 80% of whom are children, with a peak incidence between ages 2 and 14. The disease is seasonal in temperate zones, with peaks in autumn and winter. This may be explained by the breeding pattern of cats and the acquisition of pet cats.

Cats are the main reservoir of Bartonella infection in humans, although other mammals may be infected. A careful history of our patient indicated exposure to both a pet rabbit and a cat.

Serological testing for B henselae is both sensitive and specific for cat scratch disease. Such testing precludes surgical intervention. Several antibiotics have been advocated for systemic illness associated with cat scratch disease, including gentamicin, rifampicin, and ciprofloxacin. The use of antibiotics in cat scratch disease with lymphadenopathy and no systemic symptoms remains controversial, although some benefit in the reduction of lymph node size has been shown with azithromycin.¹⁰

Cat scratch disease should be considered in patients with chronic (>3 weeks) lymphadenopathy. The history taking should include contact with animals, especially scratches from mammals. Cat scratch disease may be more prevalent than realised, and an unnecessary biopsy may be avoided on the basis of serology results.

	Acknowledgments

   AW had the idea for the case report, performed the literature search, and wrote the manuscript. CDS and TR edited the manuscript and suggested improvements. CDS and TR will act as guarantors for the paper.

	Footnotes

Funding: St Thomas Medical Group Research Unit is funded by the NHS South West Regional Health Authority Research and Development Executive.

Competing interests: None declared.

	References

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10.	Bass JW, Freitas BC, Freitas AD, Sisier CL, Chan DS, Vincent JM, et al. Prospective randomised double blind placebo controlled evaluation of azithromycin for treatment of cat scratch disease. Pedr Infect Dis J 1998; 17: 447-452.

(Accepted 1 October 2001)