Clinical thinking and decision making in clinical practice. A patient with systemic lupus erythematosus and behavioral changes

: A 48-year-old man with systemic lupus erythematosus (SLE) was admitted with fever, headache and mental change. On admission he was treated with daily doses of cyclophosphamide 100 mg and prednisone 7.5 mg. Orientation and attention were diminished and visual examination revealed right-sided homonymous hemianopia. MRI of the brain showed a ring-enhanced, space occupying lesion in the left occipital lobe. An infectious disease cause was considered, because disease activity parameters of SLE were all negative (anti-dsDNA and the complement profile). The anti-Toxoplasma titre was elevated in cerebrospinal fluid (57 IU/ml) and in serum (1140 IU/ml), both IgG. A tentative diagnosis of Toxoplasma encephalitis was made and a trial anti-toxoplasmosis treatment with pyrimethamine and sulfadiazine was administered. Two weeks later the patient was normal at neurological examination and his brain MRI had greatly improved. The anti-Toxoplasma titre had dropped significantly.