PT  - JOURNAL ARTICLE
AU  - Lopez-Chiriboga, A. Sebastian
AU  - Komorowski, Lars
AU  - Kümpfel, Tania
AU  - Probst, Christian
AU  - Hinson, Shannon R.
AU  - Pittock, Sean J.
AU  - McKeon, Andrew
TI  - Metabotropic glutamate receptor type 1 autoimmunity
AID  - 10.1212/WNL.0000000000002476
DP  - 2016 Mar 15
TA  - Neurology
PG  - 1009--1013
VI  - 86
IP  - 11
4099  - http://n.neurology.org/content/86/11/1009.short
4100  - http://n.neurology.org/content/86/11/1009.full
SO  - Neurology2016 Mar 15; 86
AB  - Objective: To describe retrospectively the clinical associations of immunoglobulin G (IgG) targeting metabotropic glutamate receptor 1 (mGluR1-IgG).Methods: Specimens of 9 patients evaluated on a service basis in the Mayo Clinic Neuroimmunology Laboratory by tissue-based immunofluorescence assay (IFA) yielded a robust, synaptic immunostaining pattern consistent with mGluR1-IgG (serum, 9; CSF, 2 available). Transfected HEK293 cell-based assay (CBA) confirmed mGluR1 specificity in all 11 specimens. A further 2 patients were detected in Germany primarily by CBA.Results: The median symptom onset age for the 11 patients was 58 years (range 33–81 years); 6 were male. All 9 Mayo Clinic patients had subacute onset of cerebellar ataxia, 4 had dysgeusia, 1 had psychiatric symptoms, and 1 had cognitive impairment. All were evaluated for malignancy, but only 1 was affected (cutaneous T-cell lymphoma). One developed ataxia post–herpes zoster infection. Head MRIs were generally atrophic or normal-appearing, and CSF was inflammatory in just 1 of 5 tested, though mGluR1-IgG was detected in both specimens submitted. Five patients improved (attributable to immunotherapy in 4, spontaneously in 1), 3 stabilized (attributable to immunotherapy in 2, cancer therapy in 1), and 1 progressively declined (untreated). The 2 German patients had ataxia, but fulfilled multiple sclerosis diagnostic criteria (1 relapsing-remitting, 1 progressive). However, both had histories of hematologic malignancy (acute lymphocytic leukemia and mantle cell lymphoma), and had mGluR1-IgG detected in serum by CBA (weakly positive on tissue-based IFA).Conclusions: mGluR1 autoimmunity represents a treatable form of cerebellar ataxia. Dysgeusia may be a diagnostic clue. Paraneoplastic, parainfectious, or idiopathic causes may occur.IgG=immunoglobulin G; IFA=immunofluorescence assay; IVIg=IV immunoglobulin; mGluR1=metabotropic glutamate receptor 1; MS=multiple sclerosis