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CNS Toxoplasmosis on Biologics — SCE Rheumatology MCQ

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HardRheumatology EmergenciesCNS Toxoplasmosis on BiologicsSCE Rheumatology

A 58-year-old woman with rheumatoid arthritis has received adalimumab and methotrexate for 3 years. She develops progressive headache, confusion and left-sided weakness. MRI shows multiple ring-enhancing lesions involving the basal ganglia and corticomedullary junction, with surrounding oedema. HIV testing is negative. Toxoplasma gondii IgG is positive and IgM is negative. Biopsy of the largest lesion shows necrotising inflammation containing intracellular crescent-shaped organisms and occasional tissue cysts. Which diagnosis and explanation best fit these findings?

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Correct answer: A — Cerebral toxoplasmosis from latent T. gondii reactivation during TNF-inhibitor immunosuppression

This is cerebral toxoplasmosis, most consistent with reactivation of latent infection during TNF-inhibitor immunosuppression. Positive IgG with negative IgM supports previous exposure, while the ring-enhancing lesions and biopsy showing tachyzoite-like organisms and tissue cysts establish active CNS disease. Adalimumab is associated with serious parasitic and other opportunistic infections. PML generally produces non-enhancing white-matter lesions without marked mass effect and would demonstrate JC virus. Primary CNS lymphoma can enhance but would show malignant lymphoid cells. TNF inhibitors can be associated with demyelination, although the histology here is infectious. Cerebral tuberculomas are an important anti-TNF differential but would show granulomatous inflammation, often with caseation, rather than Toxoplasma organisms. Toxoplasma IgG alone would not have been diagnostic without the additional microbiological or pathological evidence.

Reference: Almeida GB et al. Cerebral Toxoplasmosis as an Uncommon Complication of Biologic Therapy for Rheumatoid Arthritis: Case Report and Review of the Literature. Brain Sciences. 2022;12:1050. https://pubmed.ncbi.nlm.nih.gov/36009113/