Toscana virus (TOSV) meningitis with atypical characteristics: Report of two cases

Toscana virus (TOSV) is an emerging cause of central nervous system (CNS) infections, especially in endemic countries during summer. Cerebrospinal fluid (CSF) is usually clear, with < 500 leukocytes/mm³, normal glucose (> 60 % serum glucose) and normal (< 45 mg/dL) to slightly increased protein levels. Here we present two cases of TOSV meningitis with misleading CSF characteristics observed at Santa Maria Annunziata Hospital (Bagno a Ripoli, Florence, Italy). Case 1 presented with signs and symptoms of meningitis. CSF was opalescent on macroscopic examination, with 1192 cells/mm³, hypoglycorrhachia (30 % serum glucose) and hyperproteinorachia (228.0 mg/dL). TOSV meningitis was confirmed with serology. Case 2 presented with headache, vomiting and mild neck stiffness. CSF was slightly turbid, with 1092 cells/mm³, normal glucose (61 % serum glucose) and slightly increased protein (77.0 mg/dL) levels. TOSV meningitis was confirmed with serology and molecular test on CSF. We performed a literature review including cases of TOSV neuroinvasive infections in which CSF characteristics were reported. Pleocytosis > 500 cells/mm³ was reported in 12/62 (19.4 %) patients, hypoglycorrhachia in 3/62 (4.8 %) patients, mild hyperproteinorachia (45 - 75 mg/dL) in 7/62 (11.3 %) patients and severe hyperproteinorachia (> 75 mg/dL) in 40/62 (64.5 %) patients. TOSV should be considered in the differential diagnosis of CNS infections in endemic areas during the warm season even when CSF examination shows atypical results.