Introduction

IgLON5 was recently discovered as target antigen of autoantibodies in eight patients from a newly discovered tauopathy with parasomnia and sleep breathing dysfunc-tion [1]. Here we report two new patients with these auto antibodies and their clinical features.

Findings

In April 2014, high-titer IgG autoantibodies against IgLON5 were found in two serum/CSF pairs archived in October (Pt1) and No-vember (Pt2) 2013.

The female Patient 1 (age 71) presented in May 2013 with unsteady gait, multiple oc-currences of falling, severe dementia, and depression. MRT revealed a left-sided non-recent cerebellar stroke and a thalamic le-sion. In July, the physical therapist reported periodic stagnancy and inability to react on call. EEG demonstrated elevated cerebral excitability such that antiepileptic treat-ment was started. By late September, the

[1] Sabater L, Gaig C, Gelpi E, et al. A novel non-rapid-eye movement and rapid-eye-movement parasomnia with sleep breathing disorder associated with antibodies

to IgLON5: a case series, characterisation of the antigen, and post-mortem study. Lancet Neurol 2014 Jun;13:575-586.

patient became fully dependent on a walk-ing frame, had developed dysphagia, severe vigilance deficits and total lack of a reaction on call. MRT demonstrated a progression of the thalamic lesion. CSF showed elevated IgG and oligoclonal bands as well as normal values for beta-amyloid and tau. Serum and CSF exhibited IgG autoantibodies against hippocampal and cerebellar neuronal sur-faces. A specific target antigen could not be determined at that time. After initiating immunsuppressive therapy with corticoster-oids the patient began to regain vigilance and could be mobilized in a wheelchair but still showed major cognitive deficits. In De-cember, the patient suddenly died of un-known reasons. No autopsy was conducted. The male Patient 2 (age 62) presented in October 2013 with severe myoclonus of the abdominal wall with severe insomnia resulting in marked daytime drowsines, fatigue, unsteady gait, and multiple falls. MRT revealed no abnormalities. Treatment with benzodiazepines led to minimal im-provement but also to dose-dependent vis-ual hallucinations and drowsiness. During a short stationary treatment in November,

mild lymphocytosis and slightly elevated levels of immunoglobulins were recog-nized in CSF but there were no signs of in-trathecal immunoglobulin synthesis. Beta-amyloid and tau were normal. The patient received pulsed high-dose corticosteroids following antiepileptics to symptomatically treat the myoclonus, without consistent improvement. Until April 2014, the patient additionally developed delusions and again visual hallucinations, pleurothotonus, an-terocollis, periodic dysarthria, and became fully dependent on a wheelchair. As a con-sequence of the retrospective finding of anti-IgLON5, intense immunosuppression was suggested.

Conclusion

Autoantibodies against IgLON5 are a com-plementary marker for neuroimmunologi-cal diseases. Due to the heterogeneous clinical presentation, determination of anti-IgLON5 may be considered in the differen-tial diagnosis of autoimmune encephalitis, Creutzfeldt-Jakob disease or rapidly pro-gressive neurodegenerative dementia.

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Autoantibodies against IgLON5: Two new cases

R. Bahtz1, B. Teegen1, K. Borowski1, C. Probst1, I.-M. Bloecker1, K. Fechner1,

S. Parigger2, G. Daniel2, T. Bruecke2, A.-S. Lauenstein3, B. Schrank3,

W. Stoecker1, and L. Komorowski1

1 Institute for Experimental Immunology, affiliated to EUROIMMUN AG, Luebeck, Germany2 Department of Neurology, Wilhelminenspital, Vienna, Austria

3 Department of Neurology, German Clinic for Diagnostics, Wiesbaden, Germany

Indirect immunofluorescence test using tissue cryosections and IgLON5 or control plasmid-transfected HEK cells.

Pat

ien

t 1

Hippocampus(rat)

HEK-IgLON5 HEK-IgLON5Cerebellum(rat)

HEK-Control HEK-ControlCerebellum (primate)

Pat

ien

t 2 Ser

um

1:1

00

CS

F 1:

10

Ser

um

1:1

00

Scientific presentation at the 12th Congress of the International Society of Neuroimmunology (ISNI), Mainz, Germany, November 2014