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Abstract
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.
GLOSSARY
- IgG=
- immunoglobulin G;
- IFA=
- immunofluorescence assay;
- IVIg=
- IV immunoglobulin;
- mGluR1=
- metabotropic glutamate receptor 1;
- MS=
- multiple sclerosis
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received August 27, 2015.
- Accepted in final form November 30, 2015.
- © 2016 American Academy of Neurology
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