Ankylosing spondylitis (AS), an inflammatory condition affecting axial and peripheral joints, exhibits varying prevalence worldwide. This study sought to ascertain AS incidence and prevalence in Thailand from 2017 to 2020. Utilizing national databases, individuals aged 18 and above with primary AS diagnoses (ICD-10 code M45) were identified. AS prevalence and incidence were calculated with 95% confidence intervals. The total number of AS patients was 13,292 patients in 2017. The prevalence of AS was 20.4 per 100,000 populations (95% CI 20.0–20.7) in 2017. The number of new AS cases, identified during 2018–2020, was 6784, 6805, and 6791 patients, respectively. The incidences of AS in 2018, 2019, and 2020 were comparable with the incidence of 10.4 (95% CI 10.1–10.6) per 100,000-person-years. The peak age at diagnosis was 50–59 years of age between 2018 and 2020. The number of female patients was 57.8%, 57.0%, and 57.6%, in 2018, 2019, and 2020, respectively. In conclusion, AS was relatively rare among Thais and comparable between males and females. The prevalence and incidence of AS in Thailand were identified by the Thailand Database Ministry of Public Health. The epidemiological profile of AS in Thailand might help to plan better care, workforce needs, and public health budgets.

Background/Objectives: Rapid skin thickness progression assessed using the modified Rodnan skin score (mRSS) is associated with poor outcomes in systemic sclerosis (SSc). However, the correlation between patterns of skin thickness and the onset of internal organ involvement remains unclear. This study aimed to determine the correlation between peak skin thickness progression rate (pSTPR) and the onset of internal organ involvement, particularly interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH) among Thai SSc patients. Method: A prospective cohort study with retrospective analysis was conducted on adult SSc patients who experienced the onset of their first non-Raynaud phenomenon symptoms between January 2013 and December 2020 and had at least a 2-year follow-up. Patients with an overlap syndrome were excluded from this study. The pSTPR was calculated by dividing the peak of the mRSS by the duration of disease at the peak of the mRSS. Result: A total of 509 patients were included in this study. The majority of cases were female (351; 69.0%) and comprised diffuse cutaneous SSc subsets (353 cases; 69.4%). The respective mean age and median pSTPR was 48.2 ± 11.6 years and 1.63 points/year (interquartile range 0.5–4.4). The respective median durations of disease at the onset of significant ILD (>20% extent), ILD, and mean duration of disease at the onset of PAH were 3.4 (Q1–Q3 1.4–7.7), 5.4 (Q1–Q3 2.4–9.2), and 8.0 ± 4.9 years. pSTPR was negatively correlated with disease duration at the onset of significant ILD (Rho −0.509, p < 0.001), ILD (Rho −0.480, p < 0.001), PAH (Rho −0.372, p = 0.03), and disease duration from onset to death (Rho −0.367, p = 0.03) after adjusting for age, sex, and anti-topoisomerase I. Conclusion: SSc patients with a high skin thickness progression rate reaching the maximum point of mRSS were at risk of developing early ILD, PAH, and death. The pSTPR may be used to assess individuals at risk of experiencing early onset cardiopulmonary involvement in SSc.