Severe Stiff-Person Syndrome After COVID: The First Video-Documented COVID Exacerbation and Viral Implications

Stiff-person syndrome

Stiff-person syndrome (SPS) is an autoimmune disease associated mainly with antibodies to glutamic acid decarboxylase (GAD) or to glycine, characterised by intermittent painful spasms, stiffness and rigidity of the proximal and truncal muscles. Neuro-ophthalmological and gastrointestinal symptoms also occur. The symptoms are caused by neuronal excitability due to impaired inhibitory (gamma amino butyric acid [GABA] and glycine) neurotransmission. SPS is part of a larger spectrum of GAD antibody-spectrum disorders, which overlaps with autoimmune epilepsy, cerebellar ataxia, myoclonus, progressive encephalomyelitis, rigidity and myoclonus (PERM) and limbic encephalitis. PERM is often caused by antibodies against the glycine receptor. Some SPS cases are paraneoplastic. Diagnostic delay is often associated with irreversible disability, and therefore, clinicians need a high degree of clinical suspicion to make an earlier diagnosis. This review updates the various clinical presentations that should raise suspicion of SPS and its related conditions and includes a diagnostic algorithm and various treatment strategies including immunotherapy and GABA-ergic drugs.

Stiff-person syndrome and related disorders - diagnosis, mechanisms and therapies

Stiff-person syndrome (SPS) is the prototypical and most common autoimmune neuronal hyperexcitability disorder. It presents with stiffness in the limbs and axial muscles, stiff gait with uncontrolled falls, and episodic painful muscle spasms triggered by anxiety, task-specific phobias and startle responses, collectively leading to disability. Increased awareness of SPS among patients and physicians has created concerns about diagnosis, misdiagnosis and treatment. This Review addresses the evolving diagnostic challenges in SPS and overlapping glutamic acid decarboxylase (GAD) antibody spectrum disorders, highlighting the growing number of overdiagnoses and focusing on the progress made in our understanding of SPS pathophysiology, antibodies against GAD and other inhibitory synaptic antigens, and the fundamentals of neuronal hyperexcitability. It considers the role of impaired GABAergic or glycinergic inhibition in the cortex and at multiple levels in the neuraxis; the underlying autoimmunity and involvement of GAD antibodies; immunopathogenic mechanisms beyond antibodies, including environmental triggers; familial and immunogenetic susceptibility; and potential T cell cytotoxicity. Finally, the mechanistic rationale for target-specific therapeutic interventions is presented along with the available therapeutic approaches, including enhancers of GABA signalling drugs and immunotherapies.