Cat-Scratch Disease

Dinesh Gowda, MD
Texas Tech University Health Sciences Center at the Permian Basin, Odessa, Texas

A 4-year-old boy presented with tender swelling in his right axilla that had grown progressively for 4 weeks. He had not had a fever, but he had had some loss of appetite and malaise. Initially, he had been diagnosed with pyogenic lymphadenitis at a local family clinic, and he had been treated with cefdinir without much improvement. He also reported that he had had an enlarged lymph node below his chin 2 months ago that had resolved spontaneously.

The family had 2 adult cats and a kitten at home, and the boy noted that the kitten had scratched his right hand 2 weeks before the onset of his symptoms. His past medical history was unremarkable, and his immunizations were up to date.

On physical examination, he had a healing linear scar on his right hand (A) and a tender lymph node in his right axilla measuring 4 cm in diameter (B). The rest of the examination findings were unremarkable.

The results of a complete blood count, a comprehensive metabolic panel, and tests for lactate dehydrogenase and uric acid levels were all normal, and purified protein derivative test results were negative for Mycobacterium tuberculosis. Ultrasonography of the right axilla was ordered but not performed due to patient adherence issues.

A clinical diagnosis of cat-scratch disease (CSD) was made, and the patient was treated with a 5-day course of azithromycin. Results of tests for Bartonella henselae ordered at the initial encounter subsequently showed an IgG titer of greater than 1:2,560. Results were negative for B henselae IgM. At a follow-up visit 2 weeks later, the boy’s axillary swelling had significantly decreased, and all other symptoms had resolved.

CSD is the most common cause of regional lymphadenitis in children and adolescents. It usually follows a scratch or a bite from an animal (a cat or kitten in 90% of cases) and is caused by B henselae, a Gram-negative bacterium.1 CSD is most common in autumn and winter months and is more prevalent in warm, humid climates.

The hallmark finding of CSD is regional lymphadenopathy, most commonly of the axillary lymph node. The typical presentation is a brownish red papule that develops at the site of contact 7 to 12 days after a scratch or bite from a cat. The lymph nodes often are tender, warm, and erythematous, and they eventually suppurate in 10% to 30% of cases.2 Approximately 30% of patients develop low-grade fever lasting for several days. Malaise or fatigue is noted in 25% of patients, and headache and sore throat in approximately 10% of patients.2

Parinaud oculoglandular syndrome, in which granulomatous conjunctivitis is accompanied by preauricular lymphadenopathy, accounts for the majority of atypical CSD cases. Rare cases of encephalitis, osteolytic lesions, hepatosplenic involvement, encephalopathy, and neuroretinitis also have been reported.3 B henselae can cause bacillary angiomatosis or bacillary peliosis in persons with suppressed or compromised immune systems.3

CSD can be diagnosed clinically in patients with typical signs and symptoms and a compatible exposure history. Serology tests can confirm the diagnosis, although cross-reactivity may limit interpretation in some circumstances. B henselae DNA also may be detected with polymerase chain reaction testing or culture tests of pus or lymph node aspirates. Immunofluorescence antibody assay for B henselae IgG has been shown to have a sensitivity of 88% to 100% and a specificity of 92% to 98%.2 In our patient’s case, the diagnosis was suspected clinically and confirmed serologically.

Most patients with CSD have self-limited lymphadenopathy lasting 2 to 8 weeks and do not require antibiotics, although some patients may develop disseminated disease. In one randomized controlled trial, azithromycin was shown to decrease the lymph node volume more rapidly compared with no treatment.4 Other antibiotics that have been used to treat CSD include rifampin, ciprofloxacin, trimethoprim-sulfamethoxazole, and gentamycin. CSD-associated bacillary angiomatosis and peliosis have been treated with long-term regimens of oral erythromycin or doxycycline.

References

1. Cat-scratch disease (Bartonella henselae). In: American Academy of Pediatrics. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012:269-271.

2. English R. Cat-scratch disease. Pediatr Rev. 2006;27(4):123-128.

3. Klotz SA, Ianas V, Elliott SP. Cat-scratch disease. Am Fam Physician. 2011;83(2):152-155.

4. Bass JW, Freitas BC, Freitas AD, et al. Prospective randomized double blind placebo-controlled evaluation of azithromycin for treatment of cat-scratch disease. Pediatr Infect Dis. 1998;17(6):447-452.