A 64-year-old woman with rapid neurologic decline diagnosed with encephalitis after presumed metastatic cancer.

In an era of fragmented medical care, concurrent clinical features that ultimately lead to a unified diagnosis may not be prioritized appropriately. We present a case of a 64-year-old woman referred to hematology clinic for anemia, with recent memory loss and gait disturbance. Two months later, she developed pneumonia; imaging workup showed a left renal mass. Neurologic function continued to decline precluding definitive nephrectomy. She then presented with new-onset seizure and initial neuro-imaging was reported as unremarkable. One month later, outpatient neurologic workup demonstrated new left-sided weakness which prompted hospitalization and repeat neuro-imaging, which showed a 1.7-cm right frontal lobe mass lesion with surrounding vasogenic edema. The patient ultimately underwent craniotomy with resection of the mass lesion; pathology did not show metastatic renal cell cancer, the provisional clinical diagnosis. Rather, immunostaining revealed a parasite and ultimately led to a diagnosis of encephalitis, an infection whose clinical presentation had been interpreted by healthcare providers for months to be a result of metastatic cancer.