Case report: anti-IgLON5 disease combined with paraneoplastic cerebellar degeneration with the detection of anti-sulfatide IgG antibody, masquerading as meningoencephalitis.

Objective: Anti-IgLON5 disease is a rare autoimmune mediated disease. It is mainly featured by sleep-related disturbance, parkinsonism, chorea and limb ataxia. Previous studies had clarified its clinical manifestations and predisposing genes. However, as far as we know, anti-IgLON5 disease combined with paraneoplastic cerebellar degeneration (PCD) with the detection of anti-Sulfatide IgG antibody, masquerading as meningoencephalitis had not been reported before.

Case presentation: A 57-year-old Chinese female presented with walking unsteadily for 12 days and logagnosia for 2 days and was admitted to our hospital. She had a past history of breast cancer. Magnetic resonance imaging (MRI) revealed leptomeningeal enhancement (prominent in cerebellar hemisphere). Arterial spin labeling (ASL) perfusion showed hyperperfusion in the cerebellar hemisphere and interhemispheric fissure cistern. MRI and ASL indicated the diagnosis was meningoencephalitis. However, IgG anti-IgLON5 antibody was positive in both serum and cerebrospinal fluid. Therefore, the diagnosis was anti-IgLON5 disease. In addition, the patient combined with PCD due to positive anti-Yo-antibody in serum fluid .

Conclusions: Whereas sleep disturbance is the most common feature in patients with anti-IgLON5 disease, our case presented with walking unsteadily and logagnosia. Anti-IgLON5 disease combined with PCD with the detection of anti-Sulfatide IgG antibody, masquerading as meningoencephalitis is very rare. Therefore, if meningoencephalitis did not recover with conventional treatment, anti-IgLON5 disease and PCD should be considered as the differential diagnosis.