Tumefactive demyelinating CNS lesion in a 60-year-old woman with familial Mediterranean fever

Summary We here report on a 60-year-old woman with familial Mediterranean fever (FMF) who developed cognitive impairment 16 years after initial diagnosis. On MRI, a new extensive white matter lesion in the right frontal lobe with mild local mass effect but without contrast enhancement was detectable and classified as a tumefactive lesion. Additional MR spectroscopy showed markedly increased choline levels accompanied by a significant lactate peak, highly suggestive of a low-florid demyelinating process. Although diffuse central nervous system (CNS) lesions have been described in single FMF cases, tumefactive lesions have not been observed in FMF patients without concomitant multiple sclerosis. In summary, this case highlights rare differential diagnoses of atypical, inflammatory CNS lesions and the clinical utility of MR spectroscopy.