== Patient 1: (A.a) T2-weighted images demonstrate diffuse periventricular hyperintense lesions (thick arrows, A.a). cells around blood vessels and activation of microglia without obvious features of clasmatodendrosis. == Conclusions == The GFAP-AB negative patient had both a striking (para)clinical similarity and an immediate response to immunotherapy. This supports the hypothesis that the clinical spectrum of steroid-responsive meningoencephalomyelitis suggestive of autoimmune GFAP astrocytopathy may be broader and may comprise also seronegative cases. First described in 2016, autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy has been characterized as a rare CNS disorder, typically manifesting as a steroid-responsive encephalitis, meningitis, myelitis, or meningoencephalomyelitis. Neurologic symptoms such as (sub)acute encephalopathy, blurred vision, postural tremor, and seizures often occur following an initial prodromal phase with influenza-like symptoms.1,2A characteristic feature in brain MRIs is a linear perivascular gadolinium enhancement in the white matter extending radially outward from the ventricles. In addition, extensive lesions of the spinal gray matter may be detected.1No definite diagnostic criteria have been established yet.3For diagnosis of autoimmune GFAP astrocytopathy, detection of GFAP antibodies (ABs) in the patient’s CSF or serum is required.1CSF cell count and CSF protein level are usually abnormal. Disease onset has been reported after influenza-like symptoms, a preceding herpes simplex encephalitis, and varicella zoster encephalitis, respectively.1,4Other ABs, e.g., NMDA receptor IgG and aquaporin-4 IgG may also be detected in autoimmune GFAP astrocytopathy. Furthermore, the disease can be related to an underlying malignancy, with ovarian teratoma being the most common.1The majority of patients improve after treatment with immunotherapy, especially corticosteroids.2Yet, the pathophysiology of autoimmune GFAP astrocytopathy is unknown. Here, we compare clinical, radiologic, and serologic findings of two patients with a very similar disease course suggestive of GFAP astrocytopathy. Despite intriguing similarity, only one patient harbored anti-GFAP ABs in serum and CSF. We here discuss that the characteristic clinical syndrome of autoimmune meningoencephalomyelitis with linear perivascular gadolinium enhancement Buparvaquone may not necessarily be associated with anti-GFAP ABs. == Case report 1 == During winter season, a 53-year-old Caucasian man was admitted to hospital due to influenza A infection. In the following weeks, the patient developed cognitive impairment, ataxia, tremor, and a left gazeevoked nystagmus (for details, seetable 1). Cranial MRI revealed areas with diffuse periventricular T2 hyperintensities and linear perivascular gadolinium enhancement in the supratentorial white matter extending radially outward from the ventricles (figure, A). CSF diagnostics revealed 86 cells/L and 1,075 mg/L protein. High titers of anti-GFAP IgG ABs (titer 1:320) were found in Buparvaquone CSF and serum. A typical staining pattern restricted to astrocytes could be detected after incubation of mouse brain slices and astrocyte and microglia cocultures with the patient’s CSF. A confirmatory cell-based assay with the GFAP isoform (Euroimmun, Lbeck, Germany) was positive when incubated Rabbit polyclonal to PLD3 with the patient’s CSF (figure, B). After other differential diagnoses were ruled out (table 2), autoimmune GFAP astrocytopathy was diagnosed. The patient was treated with methylprednisolone 1000 mg/d for 5 consecutive days. A rapid clinical Buparvaquone improvement and a reduction of anti-GFAP IgG AB titers (CSF 1:100, serum 1:100) could be observed. MRI follow-up revealed regressive gadolinium enhancement and decreased Buparvaquone periventricular T2 hyperintensities. In addition, EEG follow-up showed improvement with basal alpha activity. When the daily oral prednisolone dose was reduced to less than 20 mg during the following months, the patient’s condition deteriorated again as he developed tremor. We therefore initiated 6 cycles of immunoadsorption and subsequently started rituximab treatment. This led to a clinical improvement with almost complete remission of clinical symptoms within 2 weeks. == Table 1. == Clinical characteristics of Buparvaquone case reports 1 and 2 == Figure. Patients’ MRIs, immunofluorescence, and histologic findings. == Patient 1: (A.a) T2-weighted images demonstrate diffuse periventricular hyperintense lesions (thick arrows, A.a). Axial (A.b) and sagittal (A.c) T1-weighted images with gadolinium show linear perivascular enhancement extending radially.