From the Guidelines
For a 4-year-old with persistent lymphadenopathy being investigated for toxoplasmosis and cat scratch disease, recommended investigations include serological testing for both conditions, with toxoplasmosis testing prioritizing IgG and IgM antibody tests, and cat scratch disease testing focusing on Bartonella IgG and IgM antibodies, alongside PCR testing of lymph node aspirate and other supportive tests.
Key Investigations
- Serological testing for toxoplasmosis: IgG and IgM antibody tests, where positive IgM indicates acute infection and positive IgG with negative IgM suggests past infection 1.
- Serological testing for cat scratch disease (caused by Bartonella henselae): Bartonella IgG and IgM antibodies, with titers ≥1:64 considered significant 1.
- PCR testing of lymph node aspirate to detect Bartonella DNA.
- Additional helpful tests:
- Complete blood count to assess for leukocytosis.
- CRP or ESR to evaluate inflammation.
- Ultrasound or CT imaging of affected lymph nodes to characterize their appearance and rule out abscess formation.
Clinical Considerations
- A detailed history regarding cat exposure is essential, particularly noting scratches, bites, or contact with kittens.
- If lymphadenopathy persists beyond 6-8 weeks despite negative initial testing, consider lymph node biopsy to exclude other causes such as malignancy or other infections.
- These investigations are crucial as both conditions can cause prolonged lymphadenopathy in children, with cat scratch disease being particularly common in pediatric patients with a history of cat exposure 1.
From the Research
Investigations for Toxoplasmosis and Cat Scratch in a 4-Year-Old with Persistent Lymphadenopathy
- The diagnosis of peripheral lymphadenopathy in children, including those with toxoplasmosis and cat scratch disease, is mainly based on clinical grounds 2.
- Laboratory tests such as complete blood count, erythrocyte sedimentation rate, and/or c-reactive protein level, supplemented by appropriate antibody testing (e.g., Toxoplasma gondii, Bartonella henselae), can help identify the cause of lymph node enlargement 2.
- Cat scratch disease, caused by Bartonella henselae, is a common zoonotic infection that can be transmitted to humans through cat fleas or direct contact with infected cats 3, 4, 5.
- The clinical features of cat scratch disease include lymphadenopathy, usually accompanied by a papule or pustule at the site of the cat scratch, and sometimes systemic symptoms such as fever and malaise 3, 6.
- Toxoplasmosis, caused by Toxoplasma gondii, can also cause lymphadenopathy in children, and diagnosis is typically made through serological testing 2.
- In cases of persistent lymphadenopathy, a thorough diagnostic evaluation, including laboratory tests and imaging studies, may be necessary to rule out other potential causes, such as malignancy or granulomatous disease 2.
Diagnostic Approach
- For a 4-year-old child with persistent lymphadenopathy, the diagnostic approach should include:
- A thorough medical history and physical examination to identify potential exposures to cats or other animals that may carry zoonotic pathogens 2, 3, 4.
- Laboratory tests, such as complete blood count, erythrocyte sedimentation rate, and/or c-reactive protein level, to evaluate for signs of infection or inflammation 2.
- Antibody testing for Toxoplasma gondii and Bartonella henselae to diagnose toxoplasmosis and cat scratch disease, respectively 2, 3, 5.
- Imaging studies, such as ultrasound or computed tomography, to evaluate the extent of lymphadenopathy and rule out other potential causes 2.