Anti–mGluR1 antibodies

This laboratory assay detects IgG antibodies against mGluR1, a receptor essential for synaptic and cerebellar function. Metabotropic glutamate receptors (mGluRs) are G-protein-coupled receptors activated by glutamate binding, the main excitatory neurotransmitter in the CNS. There are eight mGluR subtypes (mGluR1–8), classified into three groups by molecular, pharmacologic, and signalling properties. mGluR1 and mGluR5 belong to Group I, are predominantly postsynaptic, and are implicated in learning, memory, epilepsy and pain; antibodies to these receptors are linked to several autoimmune CNS disorders.

Detection of anti-mGluR1 antibodies aids diagnosis of autoimmune encephalitis, especially the form presenting with acute/subacute cerebellar syndrome, and in some cases limbic encephalitis. Common clinical features include ataxia, dysarthria, gait instability, vertigo, nystagmus and speech disturbances; behavioural changes, cognitive impairment, seizures, dysgeusia, and dysautonomia may also occur. An underlying tumour – usually haematologic – is present in ~30% of cases. Early diagnosis and immunosuppressive therapy can reduce neurological sequelae and improve prognosis. Isolated serum positivity without neurological symptoms is insufficient for diagnosis; detecting antibodies in both serum and CSF strengthens the diagnosis. The detection of anti-mGluR1 antibodies has a high diagnostic value when typical cerebellar neurological symptoms are also present. Final diagnosis requires correlation of the clinical picture with laboratory findings.