Morvan syndrome and related disorders associated with CASPR2 antibodies

Bastien Joubert MD (

Dr. Joubert of Hospices Civils de Lyon in France has no relevant financial relationships to disclose.

)
Sergio Muniz-Castrillo MD (

Dr. Muñiz-Castrillo of Hospices Civils de Lyon in France has no relevant financial relationships to disclose.

)
Jerome Honnorat MD (

Dr. Honnorat of Hospices Civils de Lyon in France has no relevant financial relationships to disclose.

)
Francesc Graus MD PhD, editor. (

Dr. Graus, Emeritus Professor, Laboratory Clinical and Experimental Neuroimmunology, Institut D’Investigacions Biomédiques August Pi I Sunyer, Hospital Clinic, Spain, has no relevant financial relationships to disclose.

)
Originally released December 14, 2020; expires December 14, 2023

Overview

Morvan syndrome is a rare, life-threatening autoimmune disorder associated with anti-CASPR2 autoantibodies (CASPR2-Abs) (Saint-Martin et al 2018). Patients develop severe peripheral nerve hyperexcitability symptoms along with agrypnia excitata, a specific sleep disorder accompanied by behavioral disturbances and hallucinations. Clinical categorization is difficult because CASPR2-Abs are also found in autoimmune limbic encephalitis, which may feature behavioral disturbances and insomnia, as well as in acquired neuromyotonia (another peripheral nerve hyperexcitability syndrome) (Irani et al 2010). In fact, Morvan syndrome appears to have distinct clinical and immunological specificities (Muñiz-Castrillo et al 2020). Although the biology of Morvan syndrome remains poorly elucidated, progress has been made in its understanding.

Key points

 

• Morvan syndrome is a life-threatening disease characterized by severe peripheral nerve hyperexcitability, severe insomnia with encephalopathy and hallucinations (agrypnia excitata), and CASPR2-Abs.

 

• Morvan syndrome frequently associates with a malignant thymoma.

 

• Autoimmune accompaniments such as myasthenia gravis or autoimmune cytopenias are frequent.

 

• Immunomodulatory agents such as steroids and rituximab are usually efficient.

 

• Relapses may occur and generally herald malignant thymoma recurrence.

Historical note and terminology

The term “Morvan syndrome” comes from a publication in the late 19th century by French physician Augustin Morvan describing 6 patients with generalized "fibrillar contractions of the muscles," accompanied in 1 case by anxiety, sudation, and pain (Morvan 1890). In the mid-20th century, Roger and colleagues reported a series of 70 patients with a combination of confusion, visual hallucinations, sleep disorders, and severe peripheral nerve hyperexcitability symptoms, which they referred to as "syndrome de Morvan" (Roger et al 1953). A specific sleep disorder, agrypnia excitata, was later linked to this syndrome (Lugaresi and Provini 2001). Finally, Irani and colleagues described CASPR2-Abs in Morvan syndrome, acquired neuromyotonia, and autoimmune limbic encephalitis (Irani et al 2010).

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