Stiff-person syndrome (SPS) usually manifests as an autoimmune neuromuscular disorder characterised by pronounced and advancing rigidity, primarily affecting the trunk and proximal muscles. There are various clinical subtypes like classic SPS (truncal stiffness, generalised rigidity and muscle spasms), partial SPS (stiff-limb syndrome) and uncommon forms including progressive encephalomyelitis with rigidity and myoclonus. Camptocormia, defined as forward flexion of the spine in the upright position that disappears in the supine position, without fixed deformity, has been described only in two cases as an initial presentation of Anti glutamic acid decarboxylase (GAD) autoimmunity. We encountered a young male presenting with a progressive forward-leaning posture and involuntary rhythmic movements in the lower limb. Diagnostic workup included MRI, blood routines, autoimmune screening, genetic testing, lumbar puncture and electromyography. Elevated serum anti-GAD antibody levels, inflammatory CSF and certain other clinical features supported the diagnosis of SPS. Treatment involved benzodiazepines, muscle relaxants and immunotherapy with intravenous immunoglobulin. This case underscores the importance of considering immune-mediated causes, such as SPS, in patients presenting with camptocormia.

Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder characterized by progressive axial muscle stiffness, central nervous system hyperexcitability, and painful stimulus-sensitive muscle spasms. A nationwide survey performed in 2018 showed the estimated prevalence of SPS was 0.2 per 100,000 population. Most patients with SPS had antibodies against glutamic acid decarboxylase 65, followed by antibodies to the glycine receptor α-subunit. Usually, patients with SPS showed favorable outcomes; however, some studies have reported intractable SPS. Early diagnosis and aggressive immunotherapy are necessary for management of patients with SPS.

Recent advances in neuroimmunology have shed light on the pathogenic mechanisms underlying rare neuroimmunologic conditions such as myasthenia gravis (MG) and stiff person syndrome (SPS). Despite the rarity of these conditions, their complex manifestations and potential for irreversible disability necessitate effective therapeutic strategies. This chapter reviews the current understanding of the safety and efficacy of hematopoietic stem cell transplantation (HSCT) in MG and SPS. Several case reports and retrospective studies have demonstrated promising outcomes following HSCT in refractory MG and SPS, with significant clinical improvement and even discontinuation of chronic immunomodulatory therapy in some cases. Furthermore, HSCT may offer insights into the underlying pathophysiologic mechanisms of these conditions, particularly the role of cellular immunity. Although more research is needed to fully understand the impact of HSCT on disease pathology and outcomes, current evidence suggests that HSCT could be a valuable therapeutic option for patients with refractory MG and SPS.

BACKGROUND: Despite the frequent diagnostic delays of rare neurologic diseases (RND), it remains difficult to study RNDs and their comorbidities due to their rarity and hence the statistical underpowering. Affecting one to two in a million annually, stiff person syndrome (SPS) is an RND characterized by painful muscle spasms and rigidity. Leveraging underutilized electronic health records (EHR), this study showcased a machine-learning-based framework to identify clinical features that optimally characterize the diagnosis of SPS.
METHODS: A machine-learning-based feature selection approach was employed on 319 items from the past medical histories of 48 individuals (23 with a diagnosis of SPS and 25 controls) with elevated serum autoantibodies against glutamic-acid-decarboxylase-65 (anti-GAD65) in Dartmouth Health\'s EHR to determine features with the highest discriminatory power. Each iteration of the algorithm implemented a Support Vector Machine (SVM) model, generating importance scores-SHapley Additive exPlanation (SHAP) values-for each feature and removing one with the least salient. Evaluation metrics were calculated through repeated stratified cross-validation.
RESULTS: Depression, hypothyroidism, GERD, and joint pain were the most characteristic features of SPS. Utilizing these features, the SVM model attained precision of 0.817 (95% CI 0.795-0.840), sensitivity of 0.766 (95% CI 0.743-0.790), F-score of 0.761 (95% CI 0.744-0.778), AUC of 0.808 (95% CI 0.791-0.825), and accuracy of 0.775 (95% CI 0.759-0.790).
CONCLUSIONS: This framework discerned features that, with further research, may help fully characterize the pathologic mechanism of SPS: depression, hypothyroidism, and GERD may respectively represent comorbidities through common inflammatory, genetic, and dysautonomic links. This methodology could address diagnostic challenges in neurology by uncovering latent associations and generating hypotheses for RNDs.

OBJECTIVE: Antibodies against glutamic acid decarboxylase (GAD), originally associated with stiff person syndrome (SPS), define the GAD antibody-spectrum disorders that also include cerebellar ataxia, autoimmune epilepsy, limbic encephalitis, progressive encephalomyelitis with rigidity and myoclonus (PERM), and eye movement disorders, all of which are characterized by autoimmune neuronal excitability. This article elaborates on the diagnostic criteria for SPS and SPS spectrum disorders, highlights disease mimics and misdiagnoses, describes the electrophysiologic mechanisms and underlying autoimmunity of stiffness and spasms, and provides a step-by-step therapeutic scheme.
UNASSIGNED: Very-high serum GAD antibody titers are diagnostic for GAD antibody-spectrum disorders and also predict the presence of GAD antibodies in the CSF, increased intrathecal synthesis, and reduced CSF γ-aminobutyric acid (GABA) levels. Low serum GAD antibody titers or the absence of antibodies generates diagnostic challenges that require careful distinction in patients with a variety of painful spasms and stiffness, including functional neurologic disorders. Antibodies against glycine receptors, first found in patients with PERM, are seen in 13% to 15% of patients with SPS, whereas amphiphysin and gephyrin antibodies, seen in 5% of patients with SPS spectrum disorders, predict a paraneoplastic association. GAD-IgG from different SPS spectrum disorders recognizes the same dominant GAD intracellular epitope and, although the pathogenicity is unclear, is an excellent diagnostic marker. The biological basis of muscle stiffness and spasms is related to autoimmune neuronal hyperexcitability caused by impaired reciprocal γ-aminobutyric acid-mediated (GABA-ergic) inhibition, which explains the therapeutic response to GABA-enhancing agents and immunotherapies.
UNASSIGNED: It is essential to distinguish SPS spectrum disorders from disease mimics to avoid both overdiagnoses and misdiagnoses, considering that SPS is treatable if managed correctly from the outset to prevent disease progression. A step-by-step, combination therapy of GABA-enhancing medications along with immunotherapies ensures prolonged clinical benefits.

Stiff-person syndrome (SPS) is a rare neurological disorder characterized by chronic and progressive axial muscle rigidity and paroxysmal painful muscle spasms. The present case study described an SPS patient (increased anti-GAD65 antibody in serum and cerebrospinal fluid) with co-occurring Hashimoto\'s thyroiditis and decreased C3 complement levels. The clinical presentation, diagnostic approach, and treatment employed for this unique case were comprehensively described in detail. In this case, we comprehensively presented a case of SPS with co-occurring Hashimoto\'s thyroiditis and an associated decrease in serum C3 complement, as well as a discussion on the current data on this topic.

Stiff-person syndrome is a rare autoimmune disorder manifested by stiffness in the trunk and proximal limb muscles and painful muscle spasms in them. The disease is associated with the production of glutamate decarboxylase autoantibodies, an enzyme converting glutamate into gamma-aminobutyric acid. An increase of anti-GAD antibody serum levels above 10.000 IU/mL is specific for stiff-person syndrome. Our own clinical observation of a patient diagnosed with stiff-person syndrome is presented.
Синдром ригидного человека — редкое аутоиммунное заболевание, которое проявляется скованностью в мышцах туловища и проксимальных отделах конечностей, болезненными мышечными спазмами в них. Заболевание ассоциировано с выработкой аутоантител к глутамат-декарбоксилазе (GAD) — ферменту, превращающему глутамат в гамма-аминомасляную кислоту. Нарастание уровня анти-GAD-антител в сыворотке выше 10 000 МЕ/мл специфично для синдрома ригидного человека. Представлено собственное клиническое наблюдение пациентки с диагнозом синдрома ригидного человека.

UNASSIGNED: Antiglycine receptor (anti-GlyR) antibody mediates multiple immune-related diseases. This study aimed to summarize the clinical features to enhance our understanding of anti-GlyR antibody-related disease.
UNASSIGNED: By collecting clinical information from admitted patients positive for glycine receptor (GlyR) antibody, the clinical characteristics of a new patient positive for GlyR antibody were reported in this study. To obtain additional information regarding anti-GlyR antibody-linked illness, clinical data and findings on both newly reported instances in this study and previously published cases were merged and analyzed.
UNASSIGNED: A new case of anti-GlyR antibody-related progressive encephalomyelitis with rigidity and myoclonus (PERM) was identified in this study. A 20-year-old man with only positive cerebrospinal fluid anti-GlyR antibody had a good prognosis with first-line immunotherapy. The literature review indicated that the common clinical manifestations of anti-GlyR antibody-related disease included PERM or stiff-person syndrome (SPS) (n = 179, 50.1%), epileptic seizure (n = 94, 26.3%), and other neurological disorders (n = 84, 24.5%). Other neurological issues included demyelination, inflammation, cerebellar ataxia and movement disorders, encephalitis, acute psychosis, cognitive impairment or dementia, celiac disease, Parkinson\'s disease, neuropathic pain and allodynia, steroid-responsive deafness, hemiballism/tics, laryngeal dystonia, and generalized weakness included respiratory muscles. The group of PERM/SPS exhibited a better response to immunotherapy than others.
UNASSIGNED: The findings suggest the presence of multiple clinical phenotypes in anti-GlyR antibody-related disease. Common clinical phenotypes include PERM, SPS, epileptic seizure, and paraneoplastic disease. Patients with RERM/SPS respond well to immunotherapy.

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Stiff-person syndrome is rare and disabling autoimmune condition that most frequently affects women, with no real predisposition by race. Diagnosis is often arduous, which is why patients concomitantly suffer from anxiety and depression. To date, drug therapy is based on the use of benzodiazepines, barbiturates, and baclofen. Refractory cases are treated with intravenous immunoglobulin, plasmapheresis, B lymphocyte depletion with rituximab, and even the implantation of intrathecal baclofen devices. Botulinum toxin injection is frequently used, even if it still has an unclear role in the literature. Our case report aims to demonstrate the efficacy of a combined treatment of botulinum toxin and therapeutic exercise in a 65-year-old patient with biceps brachii muscle hypertonia and diffuse spasms of the axial musculature, using rating scales such as the Numeric Rating Scale (NRS) and Modified Ashworth Scale (MAS), joint range of motion (ROM) measurement, and muscle dynamic stiffness mensuration, which is performed by using the MyotonPro®. All the assessments were conducted at the first evaluation (T0), soon after the combined treatment with botulin toxin and therapeutic exercise (T1), three months (T2), six months (T3), and eight months after the botulinum toxin injection (T4). The patient demonstrated benefits for more than 6 months with no side effects. The combined therapy of botulinum toxin and therapeutic exercise had an excellent result in our patient.