Describe the epidemiology and patient characteristics of stiff person syndrome (SPS) patients seen at a large academic health system. 

SPS is a rare autoimmune disorder characterized by progressive muscle stiffness and painful spasms estimated to occur in 1-2 per million people within the United States, although large, population-based epidemiological studies are lacking. There are no formal consensus criteria for SPS. Here, we describe the epidemiology and clinical presentation of SPS in a large US health system utilizing a unique, linked data resource. 

We queried Health Data Compass (HDC), a linked dataset connecting electronic health records from a single academic health care system with the Colorado All Payers Claim Database from 2012 through 2022 for all patients ≥ 18-year-old with ICD-10 codes pertaining to Stiff Person Syndrome or Stiff-Man Syndrome [G25.82] with subsequent record review for diagnostic confirmation. The SPS diagnosis will be adjudicated and proposed diagnostic criteria will be applied to understand the sensitivity and specificity of this criteria in our cohort.

261 patients met the initial inclusion criteria. The database population over the interval was 2,802,246 persons. The prevalence for SPS was 9.3 per 100,000 persons (95% CI:(8.2, 10.4)). The mean age of patients was 51.8 years (SD=15.7), 57.5% were female, and 82.4% self-identified as Caucasian, 7.6% Black, and 10 % other. Based on our HDC dataset, 34 patients had high (> 20 nmol/L or >250 IU/mL) GAD65 antibody titers and 3 were glycine antibody positive. 5.75% of patients were on IVIG and 16.86% on rituximab. Additional record review is ongoing to confirm serostatus, evaluate immunotherapy, and characterize clinical presentation and medical comorbidities.

Understanding the true disease burden and onset of SPS is fundamental to ensuring optimal patient care. Characterizing SPS will provide an opportunity to ensure appropriate allocation of system resources and to improve upon current treatment standards.