Makindo Medical Notes

Related Subjects: |Herpes Varicella-Zoster (Shingles) Infection |Chickenpox Varicella Infection |Varicella Cerebral Vasculopathy |Herpes Viruses |Herpes Zoster Ophthalmicus (HZO) Shingles |MonkeyPox |Mumps |Measles |Rubella (German Measles) |Epstein-Barr Virus infection |Cytomegalovirus (CMV) infections |CMV retinitis infections |Toxoplasmosis

Causes focal CNS lesions and encephalopathy best seen on MRI, which improve with treatment.

About

• Toxoplasmosis is an intracellular protozoan infection caused by Toxoplasma gondii.
• Approximately 22% of the UK population are seropositive for previous exposure; over 90% of the French population are seropositive.
• T. gondii was discovered by Charles Nicolle and L. Manceaux in 1908 in a North African rodent, Ctenodactylus gondii.

Source

• Foodborne: Raw or undercooked meat.
• Zoonotic: Cats, birds, and other animals, or soil contaminated by cat feces.
• Congenital: Passed from an infected mother to the fetus.
• Other: Blood transfusion.

Risks

• Pregnancy: High risk to the fetus.
• HIV/AIDS: Seen in approximately 10% of untreated AIDS patients, particularly with CD4 < 100/mm³.
• Immunosuppressive therapy: Patients on immunosuppressants are at greater risk.

Clinical Presentation (Severity varies with gestation)

• Lymphadenopathy: Can involve cervical glands, resembling glandular fever. Often asymptomatic in immunocompetent individuals.
• Toxoplasmic Encephalitis: Presents with fever, severe headache, seizures, and focal neurological deficits, usually in immunocompromised patients (e.g., HIV-positive).
• Congenital Toxoplasmosis: Infection during pregnancy can result in fetal microcephaly, hydrocephalus, chorioretinitis, and intellectual disability.
• Systemic Toxoplasmosis: Can cause pneumonia, myocarditis, hepatitis, and CNS involvement, though rare in individuals with normal immunity.
• Ocular Toxoplasmosis: Characterized by progressive retinochoroiditis; symptoms include eye pain and visual loss.

Investigations

• Serology: Sabin–Feldman test in immunocompetent patients; fourfold rise in IgG or presence of IgM indicates acute infection.
• HIV Testing: Consider testing for HIV if immunocompromised.
• Imaging: MRI/CT to detect multiple ring-enhancing lesions in the brain (single lesions often suggest CNS lymphoma rather than toxoplasmosis).
• Pulmonary Assessment: CXR/CT to evaluate for pneumonitis resembling PCP.

Diagnostic Criteria

• Positive IgG seroconversion.
• Presence of typical clinical features, specific IgA/IgM, and elevated low-avidity IgG (<20%).
• Histologic findings on lymph node examination (epithelioid cells and follicular hyperplasia) and serologic evidence of active infection.
• Parasite isolation in culture or detection by PCR in blood or tissues.

Management

• Asymptomatic (Immunocompetent, Nonpregnant): Generally does not require treatment.
• Symptomatic or Immunocompromised: Sulfadiazine and Pyrimethamine for 6 weeks, with regular MRI and clinical reassessment.
• HIV: Initiate HAART once stable, as there is a risk of immune reconstitution inflammatory syndrome (IRIS).
• If no improvement within three weeks, consider differential diagnoses (e.g., CNS lymphoma, tuberculoma).

References

• Toxoplasmosis Overview - ResearchGate