RARE DISEASE
Classic stiff person syndrome
Classic stiff person syndrome
Classic stiff person syndrome
Synonyms: Classic SPS
Synonyms: Classic SPS
Synonyms: Classic SPS
Drug discovery
2
drugs
With orphan designations
Overview
Classic Stiff Person Syndrome (SPS) is a rare autoimmune neurological disorder characterized by progressive axial muscle rigidity, painful spasms triggered by sensory/emotional stimuli, and gait instability. Associated with glutamic acid decarboxylase (GAD-65) antibodies in ~80% of cases, it predominantly affects middle-aged women. Diagnosis combines clinical evaluation, GAD antibody testing, electromyography (showing continuous motor unit activity), and exclusion of mimics like multiple sclerosis [1][2][13]. First-line treatment includes GABA-enhancing agents (e.g., diazepam, baclofen) and immunotherapy (e.g., IVIg) [2][3][7][13].
Burden
Progressive disability: 65% require mobility aids; chronic pain/anxiety impair quality of life [5][13][18].
Mortality: ~10% risk of sudden death from respiratory failure or autonomic crises [5][13].
Healthcare utilization: Frequent falls (risk of fractures), 10% require ICU care for spasms [5][13][18].
Categories: rare endocrine diseases, rare neurological diseases
Research Papers
47 drug discovery papers about Classic stiff person syndrome, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
47 drug discovery papers about Classic stiff person syndrome, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2026-07-28 | Phenotypic Spectrum, Diagnostic Challenges, and Clinical Outcomes in Stiff Person Syndrome: A Single-Center Case Series
Introduction: Stiff-Person Syndrome (SPS) is a rare autoimmune neurological disorder characterized by progressive muscle rigidity and painful spasms, primarily affecting axial and proximal musculature. Its diagnosis can be challenging due to clinical overlap with other neurological conditions such as spasticity, dystonia, or functional movement disorders. The detection of antibodies against glutamic acid decarboxylase (anti-GAD) is a key biomarker that supports diagnosis. Methods: Two clinical cases of patients with manifestations consistent with classic SPS are described, and were evaluated in a specialized neurology service. Both patients underwent detailed clinical assessment, complementary studies, and serum testing for anti-GAD antibodies. Results: Both patients presented with progressive rigidity and fluctuating muscle spasms, predominantly involving axial musculature. After an extensive diagnostic workup, elevated anti-GAD antibody titers were documented in both cases, confirming the diagnosis of classic SPS. Treatment with medications enhancing GABAergic neurotransmission was associated with significant clinical improvement, evidenced by reduced rigidity and the decreased frequency of spasms. Conclusions: These cases highlight the importance of considering SPS in the differential diagnosis of progressive rigidity syndromes. Identification of anti-GAD antibodies is essential for diagnostic confirmation, and treatment that aims to enhance GABAergic neurotransmission can significantly improve symptoms and patient functionality.
2026-06-08 | Graph-Theoretical Approach for Predicting Physicochemical Properties of Stiff-Person Syndrome Drugs.
This work applies quantitative structure-property relationship analysis to examine molecular characteristics linked to stiffness person syndrome (SPS), a rare neurological condition marked by persistent muscle rigidity and spasmodic episodes. Topological indices such as Zagreb indices and their modification are employed to examine their correlations with key physicochemical properties. Linear, quadratic, exponential growth, and power curve fitting models are applied to identify the best correlations, focusing on the maximum F-statistic and the coefficient of determination R2. Furthermore, heatmap-based correlation analysis is performed to visually quantify the strength and direction of correlations between the calculated topological indices and selected physicochemical parameters. In addition to classical regression techniques, gradient boosting, a powerful ensemble machine learning method, is utilized to enhance predictive accuracy and evaluate the contribution of each descriptor toward property estimation. Additionally, M-polynomials are calculated, and their corresponding graphs are plotted to assess the structural features of potential therapeutic agents. The findings offer significant insights into the role of graph-theoretical methods in drug discovery, advancing the computational design of targeted treatments for SPS.
2025-06-09 | Stiff person syndrome: navigating challenges in diagnosis and treatment
Background and objectives. Stiff person syndrome (SPS) is a rare, autoimmune neurological disorder marked by progressive muscle stiffness and episodic spasms. Its low prevalence and varied presentation complicate timely diagnosis. This review synthesizes clinical, diagnostic, and therapeutic insights into SPS and its phenotypic variants, highlighting challenges in early diagnosis and management. Materials and methods. We performed a narrative review of 48 English-language publications identified through comprehensive searches of PubMed and Web of Science (up to 2025). Inclusion focused on studies addressing SPS epidemiology, clinical features, antibody associations, diagnostics, and treatments. Results. SPS affects approximately 1 in 1,000,000, predominantly women in mid-adulthood. Phenotypic variants include classic SPS (axial rigidity with anti-GAD65 antibodies in ~70–80%), focal/partial SPS, SPS-plus with ataxia (often anti-GAD or anti-GlyR), progressive encephalomyelitis with rigidity and myoclonus (PERM; frequently anti-GlyR positive), and paraneoplastic SPS (commonly anti-amphiphysin). Diagnostic challenges arise from overlap with functional, psychiatric, or movement disorders and seronegative cases (~20%). Management involves GABA-enhancing drugs for symptom relief plus immunotherapies (IVIG, plasmapheresis, rituximab), though responses are often partial. Early diagnosis and tailored immunotherapy improve function and quality of life, despite residual disability. Five summary tables detail the clinical spectrum, antibody associations, and treatment outcomes. Conclusions. SPS requires a high index of suspicion and combined symptomatic and immunotherapy for optimal management. Early recognition and treatment may improve outcomes, but residual disability is common, highlighting the need for more effective therapies. Increased awareness of phenotypes, EMG and antibody testing, and timely immunotherapy are key. Future research should develop targeted therapies to better modify disease progression.
2023-09-22 | Prevalence, Clinical Profiles, and Prognosis of Stiff-Person Syndrome in a Japanese Nationwide Survey
To elucidate current epidemiologic, clinical, and immunologic profiles and treatments of stiff-person syndrome (SPS) in Japan. A nationwide mail survey was conducted using an established method. Data processing sheets were sent to randomly selected departments of internal medicine, neurology, pediatrics, psychiatry, and neurosurgery in hospitals and clinics throughout Japan to identify patients with SPS who were seen between January 2015 and December 2017. Thirty cases were identified as glutamic acid decarboxylase 65 (GAD65)–positive SPS cases on the basis of detailed clinical data of 55 cases. Four patients had α1 subunit of glycine receptor (GlyR) antibodies, and 1 patient had both GAD65 and GlyR antibodies. The total estimated number of patients with GAD65-positive SPS was 140, and the estimated prevalence was 0.11 per 100,000 population. The median age at onset was 51 years (range, 26–83 years), and 23 (76%) were female. Of these, 70% had classic SPS, and 30% had stiff-limb syndrome. The median time from symptom onset to diagnosis was significantly longer in the high-titer GAD65 antibody group than in the low-titer group (13 months vs 2.5 months, p = 0.01). The median modified Rankin Scale (mRS) at baseline was 4, and the median mRS at the last follow-up was 2. Among the 29 GAD65-positive patients with ≥1 year follow-up, 7 received only symptomatic treatment, 9 underwent immunotherapy without long-term immunotherapy, and 13 received long-term immunotherapy such as oral prednisolone. The coexistence of type 1 diabetes mellitus and the lack of long-term immunotherapy were independent risk factors for poor outcome (mRS ≥3) in the GAD65-positive patients (odds ratio, 15.0; 95% CI 2.6–131.6; p = 0.001; odds ratio, 19.8; 95% CI 3.2–191.5; p = 0.001, respectively). This study provides the current epidemiologic and clinical status of SPS in Japan. The symptom onset to the diagnosis of SPS was longer in patients with high-titer GAD65 antibodies than in those with low-titer GAD65 antibodies. The outcome of patients with SPS was generally favorable, but more aggressive immunotherapies are necessary for GAD65-positive patients with SPS.
2021-05-10 | Case Report: Breast cancer-associated paraneoplastic stiff person syndrome: anastrozole monotherapy insufficient for symptom improvement
Stiff person syndrome (SPS) is a rare clinical disorder presenting with progressive muscle stiffness and painful spasms. Its ill-defined mechanism and variable presentation make diagnosis a challenge, though it is associated with a range of specific auto-antibodies. One particular antibody, anti-amphiphysin, is found in the presence of breast or lung malignancy and leads to a disorder termed paraneoplastic SPS (PSPS). Our patient, an 83-year-old woman, presented with bilateral leg weakness, spasms, and left clubfoot over a period of three months. She also reported a lump in her left breast for which she had not sought treatment over the past 10 years. Her ankle radiograph was negative for fractures and dislocations, while an MRI of the left leg was negative for plexopathies. Electromyography was suggestive of an SPS disorder and a positive anti-amphiphysin test indicated a diagnosis of PSPS. Her symptoms were managed with baclofen, diazepam, and five cycles of therapeutic plasma exchange (TPEX) over 10 days. Breast imaging revealed a 4.5-cm left breast lesion, later biopsy-confirmed as invasive ductal carcinoma (ER+, PR+, HER2−). The patient declined definitive surgical management, opting instead for once-daily anastrozole 1 mg as hormonal therapy. This regimen was not sufficient to lead to symptomatic improvement over a period of more than 30 days, and the patient expired less than 45 days after discharge. To our knowledge, this is the first case of PSPS to be treated in this manner. Our report illustrates that conservative management with anastrozole monotherapy was not sufficient to lead to symptomatic improvement in this form of paraneoplastic syndrome, suggesting the need for more aggressive pharmacological or definitive surgical intervention in order to produce symptom improvement and/or resolution.
antibodies
2026-04-24 | Stiff person syndrome: an overview.
BACKGROUND: Stiff-person syndrome (SPS) and stiff-person spectrum disorders (SPSD) are rare, immune-mediated neurological conditions characterized by progressive muscle rigidity, painful spasms, exaggerated startle responses, and substantial functional and psychosocial morbidity. Clinical heterogeneity, frequent diagnostic delay, and evolving immunopathogenic insights continue to complicate diagnosis and management. METHODS: This narrative review synthesizes current evidence on the epidemiology, clinical phenotypes, immunopathogenesis, diagnostic strategies, therapeutic approaches, monitoring tools, and psychosocial impact of SPS and SPSD. Evidence from randomized controlled trials, cohort studies, systematic reviews, and recent advances in immunotherapy is integrated, with attention to both adult- and pediatric-onset disease. RESULTS: Classic SPS is most commonly associated with high-titer antibodies against glutamic acid decarboxylase 65 and presents with axial and proximal limb rigidity, stimulus-sensitive spasms, hyperlordosis, and gait impairment. The SPS spectrum includes stiff limb syndrome, SPS-plus, progressive encephalomyelitis with rigidity and myoclonus, paraneoplastic SPS, and seronegative forms, each with distinct clinical and immunological profiles. Impaired GABAergic inhibition represents a central pathophysiological mechanism, although the direct pathogenic role of anti-glutamic acid decarboxylase antibodies remains debated. Diagnosis relies on characteristic clinical features, targeted autoantibody testing, and neurophysiological evidence of continuous motor unit activity. Management is anchored in symptomatic GABAergic agents and immunomodulatory therapies, with intravenous immunoglobulin supported by randomized trial evidence. Emerging treatments—including B-cell–depleting therapies, plasma exchange, autologous hematopoietic stem cell transplantation, neonatal Fc receptor blockade, and chimeric antigen receptor T-cell therapy—offer potential benefit in refractory disease. Standardized clinical scales are essential for monitoring disease burden and treatment response.
2025-08-08 | Exploring if Longitudinal Changes on PET Imaging Can Serve as a Biomarker for Stiff Person Syndrome Spectrum Disorders.
To identify metabolic patterns in the brain and musculoskeletal system of stiff person syndrome spectrum disorders (SPSD) patients over time using PET imaging and evaluate the impact of immune therapy on metabolic activity as a surrogate for treatment response. This observational study at the Johns Hopkins SPS Center of Excellence included adults (≥ 18 years) diagnosed with classic SPS, partial SPS, SPS plus, or PERM, who were treated from 2009 to 2023. Participants underwent at least two whole-body and/or dedicated brain PET scans. Brain PET analysis utilized NeuroQ v3.8 software to generate standardized Z-scores for 47 distinct brain regions, assessed by expert nuclear medicine radiologists. Patient demographics, antibody types, immune therapies, and symptomatic treatments were assessed. Eighteen patients met inclusion criteria (10 SPS plus, 6 classic SPS, 2 PERM), with a mean age of 50.7 (SD 8.5) years; 77.8% were female and 50.0% were Black/African American. Hypermetabolic activity and hypometabolism were both seen over time in the brain and the musculoskeletal system. Two patients starting immune therapy in between PET scans demonstrated improvement in brain but not body PET findings. The study findings indicate that PET imaging abnormalities are present over time and appear to have regional patterns that are common among phenotypes. Additionally, starting immune therapy between scans appears to correlate with stabilization or improvement in brain PET abnormalities, though this was less clear in body PET scans. PET scans have the potential to be an imaging biomarker in SPSD, but future studies are needed to validate this.
2025-05-09 | Clinical Features and Outcomes of Glutamic Acid Decarboxylase-65 Antibody-Associated Pure Cerebellar Ataxia and Stiff Person Syndrome Spectrum Disorders: A Single-Center Cohort Study.
Cerebellar ataxia is associated with greater disability in glutamic acid decarboxylase-65 (GAD65) antibody-associated neurological disorders and can occur in isolation or as part of stiff person syndrome (SPS) spectrum disorders (SPSD). We sought to phenotypically characterize this subpopulation with cerebellar dysfunction. Observational study of GAD65 antibody-seropositive individuals with cerebellar involvement seen at Johns Hopkins (1997-2024). Subjects were divided into two groups based on cerebellar dysfunction in the presence (SPSD; SPS-plus and progressive encephalomyelitis with rigidity and myoclonus [PERM]) or absence (pure cerebellar ataxia [pCA]) of classic SPS features. Clinical and paraclinical findings were analyzed descriptively. Seventy-two patients were selected among 356 (62 SPSD, 10 pCA). Mean age for patients with pCA was 58 ± 16 years versus 46 ± 15 years for SPSD (p = 0.012). Males comprised 50% of the pCA group versus 19% SPSD (p = 0.049). High GAD65 antibody serum titers occurred in 76% without group differences, while cerebrospinal fluid antibody positivity occurred in 35/37 (95%) of SPSD versus 5/8 (62%) pCA (p = 0.033). Although the modified Rankin scale was similar (median 3, interquartile range 2-4) in both groups, the brief ataxia rating scale indicated a higher burden of cerebellar abnormalities in pCA versus SPSD, and there was a trend toward greater cerebellar atrophy by MRI in pCA (p = 0.44). Rituximab and benzodiazepine use was more frequent in SPSD versus pCA. GAD65 antibody-associated ataxia is disabling irrespective of accompanying SPS features. Patients with pCA were older, more commonly male, and may have more frequent cerebellar atrophy than those with SPSD. Prospective validation of cerebellar outcomes and neuroimaging findings is needed.
2024-10-07 | Stiff Person Syndrome and Brittle Type 1 Diabetes: Report of 2 Cases.
Stiff person syndrome (SPS) and type 1 diabetes (T1D) are heterogeneous disorders characterized by antibodies (Abs) against glutamic acid decarboxylase (GAD). We describe 2 patients with T1D and autoimmune thyroid disease who presented with muscle rigidity and intermittent spasms that affected gait and with elevated circulating anti-GAD titers. Classic SPS and stiff limb syndrome were diagnosed, respectively. Muscle spasms resolved with immunotherapy and muscle relaxants in both patients, and the ability to ambulate without an assistive device was restored in 1 patient. Patients also had brittle diabetes with high glycemic variability, requiring the use of flash glucose monitoring with an insulin pump and a second-generation basal insulin analog, respectively. GAD Ab-associated syndromes include SPS, T1D, and other endocrinopathies. The clinical heterogeneity implies variable susceptibility of γ-aminobutyric acid-ergic neurons and pancreatic beta cells to anti-GAD or other autoantibodies. Our case series represent the heterogeneity in natural history, clinical course, and response to therapy in patients with Abs against GAD-spectrum disorders.
proteins
2025-11-03 | Botulinum toxin as a potential adjunct therapy in stiff person syndrome spectrum disorders.
Stiff person syndrome spectrum disorders (SPSD) are a disabling group of immune-mediated disorders that most commonly cause progressive rigidity and painful spasms. Botulinum neurotoxin (BoNT) has anecdotally improved SPSD symptoms, though evidence regarding treatment strategy and clinical efficacy is scarce. To characterize the location, frequency, dosage, and clinical response to BoNT injections in patients with SPSD. We conducted a retrospective observational cohort study. SPSD patients who received BoNT treatments between August 2018 and February 2024 were included. Detailed information about the injections (formulation, dose, muscle), subjective patient-reported response, and concurrent therapies was recorded and compared between the first, third, and eighth BoNT visits. Thirty-seven SPSD patients were included. The majority had classic SPS (83.8%), were female (67.7%), white (78.4%), and on immune therapies (70.3%). The paraspinal muscles, hip flexors, distal leg flexors, and shoulder girdle muscles were most frequently injected. Supramaximal total doses up to 980 units of BoNT were used safely. The most common side effect was transient worsening of pain/spasms, which resolved with peak dose effect. Subjective clinical response was positive, with a median patient-reported 5-point Likert rating of 4, 5, and 5 after visits 1, 3, and 8. BoNT may be an effective and durable adjunctive symptomatic therapy for people with SPSD with targeted muscle selection based on specific symptomatology. Injections into multiple body regions and use of supramaximal dosages may be required for adequate symptom control in this patient population. As our data lacked objective measures and relied on semiqualitative self-reported patient responses, conclusions about the utility of BoNT are limited and randomized placebo-controlled trials are needed to evaluate the impact of BoNT on improving quality of life, mobility, and burden of systemic symptomatic treatment.
small molecules
2026-07-28 | Phenotypic Spectrum, Diagnostic Challenges, and Clinical Outcomes in Stiff Person Syndrome: A Single-Center Case Series
Introduction: Stiff-Person Syndrome (SPS) is a rare autoimmune neurological disorder characterized by progressive muscle rigidity and painful spasms, primarily affecting axial and proximal musculature. Its diagnosis can be challenging due to clinical overlap with other neurological conditions such as spasticity, dystonia, or functional movement disorders. The detection of antibodies against glutamic acid decarboxylase (anti-GAD) is a key biomarker that supports diagnosis. Methods: Two clinical cases of patients with manifestations consistent with classic SPS are described, and were evaluated in a specialized neurology service. Both patients underwent detailed clinical assessment, complementary studies, and serum testing for anti-GAD antibodies. Results: Both patients presented with progressive rigidity and fluctuating muscle spasms, predominantly involving axial musculature. After an extensive diagnostic workup, elevated anti-GAD antibody titers were documented in both cases, confirming the diagnosis of classic SPS. Treatment with medications enhancing GABAergic neurotransmission was associated with significant clinical improvement, evidenced by reduced rigidity and the decreased frequency of spasms. Conclusions: These cases highlight the importance of considering SPS in the differential diagnosis of progressive rigidity syndromes. Identification of anti-GAD antibodies is essential for diagnostic confirmation, and treatment that aims to enhance GABAergic neurotransmission can significantly improve symptoms and patient functionality.
2026-06-08 | Graph-Theoretical Approach for Predicting Physicochemical Properties of Stiff-Person Syndrome Drugs.
This work applies quantitative structure-property relationship analysis to examine molecular characteristics linked to stiffness person syndrome (SPS), a rare neurological condition marked by persistent muscle rigidity and spasmodic episodes. Topological indices such as Zagreb indices and their modification are employed to examine their correlations with key physicochemical properties. Linear, quadratic, exponential growth, and power curve fitting models are applied to identify the best correlations, focusing on the maximum F-statistic and the coefficient of determination R2. Furthermore, heatmap-based correlation analysis is performed to visually quantify the strength and direction of correlations between the calculated topological indices and selected physicochemical parameters. In addition to classical regression techniques, gradient boosting, a powerful ensemble machine learning method, is utilized to enhance predictive accuracy and evaluate the contribution of each descriptor toward property estimation. Additionally, M-polynomials are calculated, and their corresponding graphs are plotted to assess the structural features of potential therapeutic agents. The findings offer significant insights into the role of graph-theoretical methods in drug discovery, advancing the computational design of targeted treatments for SPS.
2025-06-09 | Stiff person syndrome: navigating challenges in diagnosis and treatment
Background and objectives. Stiff person syndrome (SPS) is a rare, autoimmune neurological disorder marked by progressive muscle stiffness and episodic spasms. Its low prevalence and varied presentation complicate timely diagnosis. This review synthesizes clinical, diagnostic, and therapeutic insights into SPS and its phenotypic variants, highlighting challenges in early diagnosis and management. Materials and methods. We performed a narrative review of 48 English-language publications identified through comprehensive searches of PubMed and Web of Science (up to 2025). Inclusion focused on studies addressing SPS epidemiology, clinical features, antibody associations, diagnostics, and treatments. Results. SPS affects approximately 1 in 1,000,000, predominantly women in mid-adulthood. Phenotypic variants include classic SPS (axial rigidity with anti-GAD65 antibodies in ~70–80%), focal/partial SPS, SPS-plus with ataxia (often anti-GAD or anti-GlyR), progressive encephalomyelitis with rigidity and myoclonus (PERM; frequently anti-GlyR positive), and paraneoplastic SPS (commonly anti-amphiphysin). Diagnostic challenges arise from overlap with functional, psychiatric, or movement disorders and seronegative cases (~20%). Management involves GABA-enhancing drugs for symptom relief plus immunotherapies (IVIG, plasmapheresis, rituximab), though responses are often partial. Early diagnosis and tailored immunotherapy improve function and quality of life, despite residual disability. Five summary tables detail the clinical spectrum, antibody associations, and treatment outcomes. Conclusions. SPS requires a high index of suspicion and combined symptomatic and immunotherapy for optimal management. Early recognition and treatment may improve outcomes, but residual disability is common, highlighting the need for more effective therapies. Increased awareness of phenotypes, EMG and antibody testing, and timely immunotherapy are key. Future research should develop targeted therapies to better modify disease progression.
2023-09-22 | Prevalence, Clinical Profiles, and Prognosis of Stiff-Person Syndrome in a Japanese Nationwide Survey
To elucidate current epidemiologic, clinical, and immunologic profiles and treatments of stiff-person syndrome (SPS) in Japan. A nationwide mail survey was conducted using an established method. Data processing sheets were sent to randomly selected departments of internal medicine, neurology, pediatrics, psychiatry, and neurosurgery in hospitals and clinics throughout Japan to identify patients with SPS who were seen between January 2015 and December 2017. Thirty cases were identified as glutamic acid decarboxylase 65 (GAD65)–positive SPS cases on the basis of detailed clinical data of 55 cases. Four patients had α1 subunit of glycine receptor (GlyR) antibodies, and 1 patient had both GAD65 and GlyR antibodies. The total estimated number of patients with GAD65-positive SPS was 140, and the estimated prevalence was 0.11 per 100,000 population. The median age at onset was 51 years (range, 26–83 years), and 23 (76%) were female. Of these, 70% had classic SPS, and 30% had stiff-limb syndrome. The median time from symptom onset to diagnosis was significantly longer in the high-titer GAD65 antibody group than in the low-titer group (13 months vs 2.5 months, p = 0.01). The median modified Rankin Scale (mRS) at baseline was 4, and the median mRS at the last follow-up was 2. Among the 29 GAD65-positive patients with ≥1 year follow-up, 7 received only symptomatic treatment, 9 underwent immunotherapy without long-term immunotherapy, and 13 received long-term immunotherapy such as oral prednisolone. The coexistence of type 1 diabetes mellitus and the lack of long-term immunotherapy were independent risk factors for poor outcome (mRS ≥3) in the GAD65-positive patients (odds ratio, 15.0; 95% CI 2.6–131.6; p = 0.001; odds ratio, 19.8; 95% CI 3.2–191.5; p = 0.001, respectively). This study provides the current epidemiologic and clinical status of SPS in Japan. The symptom onset to the diagnosis of SPS was longer in patients with high-titer GAD65 antibodies than in those with low-titer GAD65 antibodies. The outcome of patients with SPS was generally favorable, but more aggressive immunotherapies are necessary for GAD65-positive patients with SPS.
2021-05-10 | Case Report: Breast cancer-associated paraneoplastic stiff person syndrome: anastrozole monotherapy insufficient for symptom improvement
Stiff person syndrome (SPS) is a rare clinical disorder presenting with progressive muscle stiffness and painful spasms. Its ill-defined mechanism and variable presentation make diagnosis a challenge, though it is associated with a range of specific auto-antibodies. One particular antibody, anti-amphiphysin, is found in the presence of breast or lung malignancy and leads to a disorder termed paraneoplastic SPS (PSPS). Our patient, an 83-year-old woman, presented with bilateral leg weakness, spasms, and left clubfoot over a period of three months. She also reported a lump in her left breast for which she had not sought treatment over the past 10 years. Her ankle radiograph was negative for fractures and dislocations, while an MRI of the left leg was negative for plexopathies. Electromyography was suggestive of an SPS disorder and a positive anti-amphiphysin test indicated a diagnosis of PSPS. Her symptoms were managed with baclofen, diazepam, and five cycles of therapeutic plasma exchange (TPEX) over 10 days. Breast imaging revealed a 4.5-cm left breast lesion, later biopsy-confirmed as invasive ductal carcinoma (ER+, PR+, HER2−). The patient declined definitive surgical management, opting instead for once-daily anastrozole 1 mg as hormonal therapy. This regimen was not sufficient to lead to symptomatic improvement over a period of more than 30 days, and the patient expired less than 45 days after discharge. To our knowledge, this is the first case of PSPS to be treated in this manner. Our report illustrates that conservative management with anastrozole monotherapy was not sufficient to lead to symptomatic improvement in this form of paraneoplastic syndrome, suggesting the need for more aggressive pharmacological or definitive surgical intervention in order to produce symptom improvement and/or resolution.
antibodies
2026-04-24 | Stiff person syndrome: an overview.
BACKGROUND: Stiff-person syndrome (SPS) and stiff-person spectrum disorders (SPSD) are rare, immune-mediated neurological conditions characterized by progressive muscle rigidity, painful spasms, exaggerated startle responses, and substantial functional and psychosocial morbidity. Clinical heterogeneity, frequent diagnostic delay, and evolving immunopathogenic insights continue to complicate diagnosis and management. METHODS: This narrative review synthesizes current evidence on the epidemiology, clinical phenotypes, immunopathogenesis, diagnostic strategies, therapeutic approaches, monitoring tools, and psychosocial impact of SPS and SPSD. Evidence from randomized controlled trials, cohort studies, systematic reviews, and recent advances in immunotherapy is integrated, with attention to both adult- and pediatric-onset disease. RESULTS: Classic SPS is most commonly associated with high-titer antibodies against glutamic acid decarboxylase 65 and presents with axial and proximal limb rigidity, stimulus-sensitive spasms, hyperlordosis, and gait impairment. The SPS spectrum includes stiff limb syndrome, SPS-plus, progressive encephalomyelitis with rigidity and myoclonus, paraneoplastic SPS, and seronegative forms, each with distinct clinical and immunological profiles. Impaired GABAergic inhibition represents a central pathophysiological mechanism, although the direct pathogenic role of anti-glutamic acid decarboxylase antibodies remains debated. Diagnosis relies on characteristic clinical features, targeted autoantibody testing, and neurophysiological evidence of continuous motor unit activity. Management is anchored in symptomatic GABAergic agents and immunomodulatory therapies, with intravenous immunoglobulin supported by randomized trial evidence. Emerging treatments—including B-cell–depleting therapies, plasma exchange, autologous hematopoietic stem cell transplantation, neonatal Fc receptor blockade, and chimeric antigen receptor T-cell therapy—offer potential benefit in refractory disease. Standardized clinical scales are essential for monitoring disease burden and treatment response.
2025-08-08 | Exploring if Longitudinal Changes on PET Imaging Can Serve as a Biomarker for Stiff Person Syndrome Spectrum Disorders.
To identify metabolic patterns in the brain and musculoskeletal system of stiff person syndrome spectrum disorders (SPSD) patients over time using PET imaging and evaluate the impact of immune therapy on metabolic activity as a surrogate for treatment response. This observational study at the Johns Hopkins SPS Center of Excellence included adults (≥ 18 years) diagnosed with classic SPS, partial SPS, SPS plus, or PERM, who were treated from 2009 to 2023. Participants underwent at least two whole-body and/or dedicated brain PET scans. Brain PET analysis utilized NeuroQ v3.8 software to generate standardized Z-scores for 47 distinct brain regions, assessed by expert nuclear medicine radiologists. Patient demographics, antibody types, immune therapies, and symptomatic treatments were assessed. Eighteen patients met inclusion criteria (10 SPS plus, 6 classic SPS, 2 PERM), with a mean age of 50.7 (SD 8.5) years; 77.8% were female and 50.0% were Black/African American. Hypermetabolic activity and hypometabolism were both seen over time in the brain and the musculoskeletal system. Two patients starting immune therapy in between PET scans demonstrated improvement in brain but not body PET findings. The study findings indicate that PET imaging abnormalities are present over time and appear to have regional patterns that are common among phenotypes. Additionally, starting immune therapy between scans appears to correlate with stabilization or improvement in brain PET abnormalities, though this was less clear in body PET scans. PET scans have the potential to be an imaging biomarker in SPSD, but future studies are needed to validate this.
2025-05-09 | Clinical Features and Outcomes of Glutamic Acid Decarboxylase-65 Antibody-Associated Pure Cerebellar Ataxia and Stiff Person Syndrome Spectrum Disorders: A Single-Center Cohort Study.
Cerebellar ataxia is associated with greater disability in glutamic acid decarboxylase-65 (GAD65) antibody-associated neurological disorders and can occur in isolation or as part of stiff person syndrome (SPS) spectrum disorders (SPSD). We sought to phenotypically characterize this subpopulation with cerebellar dysfunction. Observational study of GAD65 antibody-seropositive individuals with cerebellar involvement seen at Johns Hopkins (1997-2024). Subjects were divided into two groups based on cerebellar dysfunction in the presence (SPSD; SPS-plus and progressive encephalomyelitis with rigidity and myoclonus [PERM]) or absence (pure cerebellar ataxia [pCA]) of classic SPS features. Clinical and paraclinical findings were analyzed descriptively. Seventy-two patients were selected among 356 (62 SPSD, 10 pCA). Mean age for patients with pCA was 58 ± 16 years versus 46 ± 15 years for SPSD (p = 0.012). Males comprised 50% of the pCA group versus 19% SPSD (p = 0.049). High GAD65 antibody serum titers occurred in 76% without group differences, while cerebrospinal fluid antibody positivity occurred in 35/37 (95%) of SPSD versus 5/8 (62%) pCA (p = 0.033). Although the modified Rankin scale was similar (median 3, interquartile range 2-4) in both groups, the brief ataxia rating scale indicated a higher burden of cerebellar abnormalities in pCA versus SPSD, and there was a trend toward greater cerebellar atrophy by MRI in pCA (p = 0.44). Rituximab and benzodiazepine use was more frequent in SPSD versus pCA. GAD65 antibody-associated ataxia is disabling irrespective of accompanying SPS features. Patients with pCA were older, more commonly male, and may have more frequent cerebellar atrophy than those with SPSD. Prospective validation of cerebellar outcomes and neuroimaging findings is needed.
2024-10-07 | Stiff Person Syndrome and Brittle Type 1 Diabetes: Report of 2 Cases.
Stiff person syndrome (SPS) and type 1 diabetes (T1D) are heterogeneous disorders characterized by antibodies (Abs) against glutamic acid decarboxylase (GAD). We describe 2 patients with T1D and autoimmune thyroid disease who presented with muscle rigidity and intermittent spasms that affected gait and with elevated circulating anti-GAD titers. Classic SPS and stiff limb syndrome were diagnosed, respectively. Muscle spasms resolved with immunotherapy and muscle relaxants in both patients, and the ability to ambulate without an assistive device was restored in 1 patient. Patients also had brittle diabetes with high glycemic variability, requiring the use of flash glucose monitoring with an insulin pump and a second-generation basal insulin analog, respectively. GAD Ab-associated syndromes include SPS, T1D, and other endocrinopathies. The clinical heterogeneity implies variable susceptibility of γ-aminobutyric acid-ergic neurons and pancreatic beta cells to anti-GAD or other autoantibodies. Our case series represent the heterogeneity in natural history, clinical course, and response to therapy in patients with Abs against GAD-spectrum disorders.
proteins
2025-11-03 | Botulinum toxin as a potential adjunct therapy in stiff person syndrome spectrum disorders.
Stiff person syndrome spectrum disorders (SPSD) are a disabling group of immune-mediated disorders that most commonly cause progressive rigidity and painful spasms. Botulinum neurotoxin (BoNT) has anecdotally improved SPSD symptoms, though evidence regarding treatment strategy and clinical efficacy is scarce. To characterize the location, frequency, dosage, and clinical response to BoNT injections in patients with SPSD. We conducted a retrospective observational cohort study. SPSD patients who received BoNT treatments between August 2018 and February 2024 were included. Detailed information about the injections (formulation, dose, muscle), subjective patient-reported response, and concurrent therapies was recorded and compared between the first, third, and eighth BoNT visits. Thirty-seven SPSD patients were included. The majority had classic SPS (83.8%), were female (67.7%), white (78.4%), and on immune therapies (70.3%). The paraspinal muscles, hip flexors, distal leg flexors, and shoulder girdle muscles were most frequently injected. Supramaximal total doses up to 980 units of BoNT were used safely. The most common side effect was transient worsening of pain/spasms, which resolved with peak dose effect. Subjective clinical response was positive, with a median patient-reported 5-point Likert rating of 4, 5, and 5 after visits 1, 3, and 8. BoNT may be an effective and durable adjunctive symptomatic therapy for people with SPSD with targeted muscle selection based on specific symptomatology. Injections into multiple body regions and use of supramaximal dosages may be required for adequate symptom control in this patient population. As our data lacked objective measures and relied on semiqualitative self-reported patient responses, conclusions about the utility of BoNT are limited and randomized placebo-controlled trials are needed to evaluate the impact of BoNT on improving quality of life, mobility, and burden of systemic symptomatic treatment.
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Drug Discovery Landscape
2 orphan drug designations for Classic stiff person syndrome.
2 orphan drug designations for Classic stiff person syndrome.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
autologous T cells transduced with lentiviral vector containing a chimeric antigen receptor directed against CD19 | cell therapies | FDA | 2024-08-21 | — | Kyverna Therapeutics, Inc |
Intravenous immune globulin (human) 10% | antibodies | FDA | 2008-07-31 | — | Octapharma USA, Inc. |
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