Derm Dx: Swelling in the Finger Following a Cat Scratch

Based on her history, the patient was diagnosed with early cat scratch disease, also known as bartonellosis, which is a disorder that results from a cat scratch or bite. Patients may present with fever and regional lymphadenopathy; more severe cases...

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Based on her history, the patient was diagnosed with early cat scratch disease, also known as bartonellosis, which is a disorder that results from a cat scratch or bite. Patients may present with fever and regional lymphadenopathy; more severe cases may involve the cutaneous and lymphatic systems as well as visceral organs. Cat scratch disease is caused by the bacteria Bartonella henselae. Transmission occurs when a vector, the cat flea, first infects the cat and causes subsequent bacteremia, after which a cat scratch or bite spreads the disease to the human host.^1,2 Infections are more common in the fall and winter months when domestic cats are breeding, and more than half of all cases are seen in patients younger than 18 years old.²

Signs and symptoms of cat scratch disease vary widely depending on acuity and immune status. In mild cases a self-limiting fever and local lymphadenopathy may be the only symptoms, whereas immunocompromised patients can develop systemic involvement.³ Cutaneous manifestation begins as an erythematous papule, vesicle, or nodule that can persist for several weeks’ duration. Lymphadenopathy may occur proximal to the inoculation site and can persist up to 4 months.² In the event of systemic infection, symptoms such as abdominal pain (associated with liver and spleen involvement) and optic neuritis (if inoculation occurs within the conjunctiva) can arise.^2,3 

Diagnosis is often made presumptively based on history and physical examination, especially when the patient reports close contact with a cat. Serologic testing may be considered, but as B henselae can be difficult to culture, a negative result would not rule out the disease.^2,4 Treatment of cat scratch disease ranges from simple supportive care to antibiotic regimens. In mild cases, patients can be treated with antipyretics, anti-inflammatories, and warm compresses applied to the inoculation site. In moderate cases, a 5-day course of azithromycin should be considered. In immunocompromised patients, treatment with rifampin, trimethoprim-sulfamethoxazole, or ciprofloxacin may be required.²

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References

1. Hansmann Y, DeMartino S, Piémont Y, et al. Diagnosis of cat scratch disease with detection of Bartonella henselae by PCR: a study of patients with lymph node enlargement. J Clin Microbiol.  2005;43(8):3800-3806.
2. Baranowski K, Huang B. Cat scratch disease. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2018.
3. Mazur-Melewska K, Mania A, Kemnitz P, Figlerowicz M, Służewski W. Cat-scratch disease: a wide spectrum of clinical pictures. Postepy Dermatol Alergol.  2015;32(3):216-220.
4. Windsor JJ. Cat-scratch disease: epidemiology, etiology, and treatment. Br J Biomed Sci. . 2011;58(2):101-110.