The spectrum of anti-GQ1B antibody syndrome: beyond Miller Fisher syndrome and Bickerstaff brainstem encephalitis.

INTRODUCTION: Since the initial identification of Miller Fisher syndrome (MFS) and Bickerstaff brainstem encephalitis (BBE),significant milestones have been achieved in understanding these diseases.Discoveries of common serum antibodies (IgG anti-GQ1b), antecedent infections, neurophysiological data, andneuroimaging suggested a shared autoimmune pathogenetic mechanism rather than distinct pathogenesis, leadingto the hypothesis that both diseases are part of a unified syndrome, termed "Fisher-Bickerstaff syndrome". The subsequent identification of atypical anti-GQ1b-positive forms expanded the classification to a broader condition known as "Anti-GQ1b-Antibody syndrome". METHODS: An exhaustive literature review was conducted, analyzing a substantial body of research spanning from the initialdescriptions of the syndrome's components to recent developments in diagnostic classification and researchperspectives. RESULTS: Anti-GQ1b syndrome encompasses a continuous spectrum of conditions defined by a common serological profilewith varying degrees of peripheral (PNS) and central nervous system (CNS) involvement. MFS and BBE represent theopposite ends of this spectrum, with MFS primarily affecting the PNS and BBE predominantly involving the CNS.Recently identified atypical forms, such as acute ophthalmoparesis, acute ataxic neuropathy withoutophthalmoparesis, Guillain-Barré syndrome (GBS) with ophthalmoparesis, MFS-GBS and BBE-GBS overlap syndromes,have broadened this spectrum. CONCLUSION: This work aims to provide an extensive, detailed, and updated overview of all aspects of the anti-GQ1b syndromewith the intention of serving as a stepping stone for further shaping thereof. Special attention was given to therecently identified atypical forms, underscoring their significance in redefining the boundaries of the syndrome.

Anti-pan-neurofascin nodopathy: cause of fulminant neuropathy.

Autoimmune nodopathies are inflammatory diseases of the peripheral nervous system with clinical and neurophysiological peculiar characteristics. In this nosological category, we find patients with autoantibodies against Neurofascin 140/186 and 155, Contactin1, and Caspr1 directed precisely towards nodal and paranodal structures. These antibodies are extremely rare and cause severe clinical symptoms. We describe the clinical case of a patient with autoimmune nodopathy caused by the coexistence of anti-neurofascin (NF) 186/140 and 155, characterized by progressive weakness in all limbs leading to tetraplegia, involving cranial nerves, and respiratory insufficiency. Response to first-line treatments was good followed by rapid dramatic clinical relapse. There are few reported cases of anti-pan NF neuropathy in the literature, and they present a clinical phenotype similar to our patient. In these cases, early recognition of clinical red flags of nodopathies and serial neurophysiological studies can facilitate the diagnosis. However, the severe clinical relapse suggests a possible early use of immunosuppressive therapies for this rare category of patients.