Toxoplasma Lymphadenitis

Toxoplasma lymphadenitis is the commonest clinical form of acquired toxoplasmosis in immunocompetent people, caused by Toxoplasma gondii acquired from undercooked meat, cat faeces, contaminated soil or water. Most infections are asymptomatic; lymphadenopathy occurs in about 10 to 20 percent of those infected.

• Highest prevalence of infection in warm, humid regions including Kenya.
• Disease resolves spontaneously, but diagnosis matters in pregnancy and for exclusion of lymphoma.

Painless, non suppurative, discrete rubbery cervical lymph nodes (posterior cervical most commonly), sometimes with fever, malaise, myalgia, sore throat, rash and mild hepatosplenomegaly, lasting weeks to months.

• Differential diagnosis: infectious mononucleosis (EBV), CMV infection, tuberculous lymphadenitis, HIV, lymphoma, sarcoidosis, cat scratch disease, brucellosis, secondary syphilis, Kikuchi disease, metastatic cancer.
• Complications: prolonged fatigue, chorioretinitis, congenital infection after primary infection in pregnancy, dissemination (pneumonitis, myocarditis, meningoencephalitis) in immunosuppression.

Serology and tissue.

• IgM and IgG with IgG avidity (high avidity excludes infection in the previous 3 to 4 months); IgM positive needs confirmation; PCR of blood or tissue.
• Lymph node biopsy: reactive follicular hyperplasia with epithelioid histiocyte clusters and monocytoid B cells (triad).
• HIV test, full blood count with atypical lymphocytes, EBV and CMV serology, chest radiograph.

Most immunocompetent adults need only observation.

• Supportive: reassure, paracetamol 1 g four times daily, avoid raw or undercooked meat, wash fruits and vegetables, wash hands after gardening, avoid cat litter in pregnancy.
• Pharmacological: no treatment for mild illness in non pregnant immunocompetent patients. For severe or persistent symptoms, ocular or visceral involvement: pyrimethamine 200 mg loading dose then 50 mg daily (75 mg for 60 kg and over) with sulfadiazine 1 g four times daily (1.5 g for 60 kg and over) and folinic acid 10 to 25 mg daily for 2 to 4 weeks; alternative cotrimoxazole 960 mg twice daily. Pregnancy with recent infection: spiramycin 1 g (3 million units) orally three times daily until fetal infection is excluded; if amniotic fluid PCR is positive after 18 weeks, change to pyrimethamine 50 mg daily with sulfadiazine 3 g daily in divided doses and folinic acid 10 to 25 mg daily. Immunocompromised: treat for active toxoplasmosis.
• Procedures: lymph node biopsy where diagnosis is uncertain; amniocentesis for PCR (from 18 weeks).
• Special groups: pregnancy, spiramycin and fetal assessment (monthly ultrasound); HIV, give the full course for toxoplasmosis disease and start antiretroviral therapy; infants, specialist paediatric review; sulfa allergy, clindamycin 600 mg four times daily with pyrimethamine.
• Red flags: visual loss or eye pain, neurological symptoms, persistent fever, enlarging or hard nodes, pregnancy, CD4 under 100.
• Follow-up: review at 4 to 6 weeks; repeat serology at 3 weeks if pregnant; biopsy if nodes fail to regress at 3 months.