Overview
Definition:
Cat-scratch disease (CSD) is a bacterial infection caused by Bartonella henselae, typically transmitted to humans through a scratch or bite from an infected cat, or via a flea bite
It is characterized by regional lymphadenopathy.
Epidemiology:
CSD is the most common cause of chronic regional lymphadenopathy in immunocompetent children and adolescents
The incidence is estimated at 0.7 to 1.1 per 100,000 population
Cats, especially kittens, are the primary reservoir, with infection being more common in warmer months.
Clinical Significance:
While often self-limiting, CSD can lead to significant morbidity if not recognized, particularly in immunocompromised individuals or when complications arise
Understanding azithromycin indications is crucial for effective management in pediatric practice.
Clinical Presentation
Symptoms:
Initial inoculation lesion at the site of scratch or bite, often a papule or pustule, appearing 3-14 days post-exposure
Regional lymphadenopathy, typically unilateral and tender, developing 1-3 weeks later
Systemic symptoms may include fever, malaise, headache, and anorexia.
Signs:
Physical examination reveals enlarged, tender lymph nodes in the drainage area of the inoculation site
The overlying skin may be erythematous
Bacillary angiomatosis, peliosis hepatis, or endocarditis can occur in immunocompromised patients.
Diagnostic Criteria:
Diagnosis is based on a combination of clinical findings (history of cat contact, inoculation lesion, regional lymphadenopathy) and serological confirmation (indirect immunofluorescence assay [IFA] for anti-Bartonella henselae IgG antibodies
a titer of ≥1:256 is suggestive)
PCR can also be used to detect Bartonella DNA in lymph node aspirates or tissue.
Diagnostic Approach
History Taking:
Detailed history of animal contact, especially cats (recent scratches, bites, exposure to kittens)
Inquire about travel history, immunocompromise, and any signs of disseminated disease
Duration and character of lymphadenopathy are important.
Physical Examination:
Palpate for enlarged lymph nodes, noting location, size, tenderness, and consistency
Examine the skin for inoculation lesions
Assess for systemic signs like fever and hepatosplenomegaly.
Investigations:
Serology (IFA for B
henselae antibodies) is the primary diagnostic test
Complete blood count (CBC) may show mild leukocytosis or lymphocytosis
Biopsy and aspiration of affected lymph nodes for Gram stain, culture, and PCR are reserved for severe or atypical cases
Histopathology of lymph nodes typically shows granulomatous inflammation.
Differential Diagnosis:
Tuberculosis, tularemia, plague, brucellosis, fungal infections (e.g., sporotrichosis), other bacterial lymphadenitis (e.g., Streptococcus, Staphylococcus), viral infections (e.g., Epstein-Barr virus), and malignancy (lymphoma).
Management
Initial Management:
For uncomplicated CSD in immunocompetent children, symptomatic and supportive care is often sufficient
This includes analgesics for pain and antipyretics for fever
Aspiration of severely fluctuant lymph nodes may provide symptomatic relief but is not curative.
Medical Management:
Antibiotic therapy is indicated for severe disease (e.g., systemic symptoms, involvement of multiple lymph node chains, complications) or in immunocompromised patients
Azithromycin is a preferred agent due to its excellent tissue penetration and favorable pharmacokinetics
Recommended azithromycin dosage for children is 10-12 mg/kg/day (maximum 500 mg) given once daily for 5-7 days
Other agents include clarithromycin, erythromycin, rifampin, trimethoprim-sulfamethoxazole, and ciprofloxacin, typically for longer durations (2-4 weeks) and in combination for disseminated forms.
Surgical Management:
Surgical intervention is generally not indicated for typical CSD
Lymph node excision is not recommended as it may delay healing
Incision and drainage are reserved for very large, fluctuant nodes to relieve pressure, but should not be considered definitive treatment.
Supportive Care:
Adequate rest and hydration are important
Pain management with acetaminophen or ibuprofen
Close monitoring of lymphadenopathy and systemic symptoms
Education of parents regarding the benign course and potential for recurrence is essential.
Complications
Early Complications:
Suppurative lymphadenitis requiring aspiration or drainage
Parinaud's oculoglandular syndrome (conjunctivitis with preauricular lymphadenopathy)
Neurological complications (e.g., encephalopathy, seizures, optic neuritis) are rare but serious.
Late Complications:
Chronic lymphadenopathy persisting for months
Bacillary angiomatosis (vascular proliferative lesions) and peliosis hepatis in immunocompromised hosts
Endocarditis, particularly in patients with pre-existing valvular heart disease.
Prevention Strategies:
Avoid rough play with cats, especially kittens
Promptly wash any cat scratches or bites with soap and water
Keep cats free from fleas
Prompt veterinary care for cats with signs of illness.
Prognosis
Factors Affecting Prognosis:
Immunocompetence is the most significant factor
Immunocompromised patients have a higher risk of severe and disseminated disease.
Outcomes:
In immunocompetent individuals, CSD typically resolves spontaneously within 2-6 months, even without antibiotic therapy
With appropriate antibiotic treatment, especially azithromycin, recovery is usually prompt with resolution of lymphadenopathy and systemic symptoms.
Follow Up:
Follow-up is generally not required for uncomplicated cases
Patients with severe disease, immunocompromise, or complications should be monitored closely until full recovery
Recurrence is rare.
Key Points
Exam Focus:
Recognize CSD as a common cause of chronic lymphadenopathy in children
Identify the typical inoculation lesion and regional lymphadenopathy pattern
Recall azithromycin as the drug of choice for severe or complicated cases
Know the typical antibiotic dosage for azithromycin in pediatrics.
Clinical Pearls:
Always ask about cat exposure in pediatric patients presenting with lymphadenopathy
Consider serology for Bartonella henselae
Empiric antibiotics are usually not necessary for mild, uncomplicated cases, but are crucial for severe presentations and immunocompromised individuals.
Common Mistakes:
Over-reliance on lymph node biopsy for diagnosis in typical cases
Delaying appropriate antibiotic treatment in immunocompromised patients or those with severe systemic symptoms
Aggressive surgical management of lymph nodes when conservative measures suffice.