The MAPSI project is a non-profit, multicenter, cross-sectional, and observational study, explicitly designed as non-retrospective, designed to investigate the prevalence of PsA in Italy. The study was conducted across twenty-five Rheumatology Units in Italy, recruiting patients from both hospital-based and outpatient clinics; see the Supplementary material for information on enrollment centers and patient numbers per center. Data were collected concurrently with patient evaluations, beginning with an initial baseline visit (T0) and, where applicable, a follow-up visit to monitor clinical progression.

Patients with a diagnosis of PsA, either formulated or confirmed by a rheumatologist, were enrolled in the study. Recruitment from a variety of clinical settings aimed to achieve a representative sample of the Italian PsA population. Inclusion criteria mandated a confirmed PsA diagnosis by a rheumatologist, ensuring that all cases met standard clinical practice guidelines.

The study protocol was approved by the Ethics Committee of each participating center, in compliance with ethical guidelines for research. All patients provided written informed consent before enrollment, confirming their willingness to participate in the study and allowing the use of their data for research purposes.

At T0 treating physicians collected a comprehensive set of demographic, clinical, therapeutic, clinimetric indices and laboratory data for each patient. Baseline demographic data included gender, age, body mass index (BMI), and smoking status.

Disease-specific data were collected through an in-depth anamnesis to ensure accuracy and detail. All data were systematically recorded using case report forms (CRFs) to standardize data collection across centers. We documented data concerning the onset of psoriatic arthritis, including age at disease onset, disease duration at the time of diagnosis, and symptom duration prior to diagnosis. Clinical presentation was documented based on physician-assessed joint counts for peripheral arthritis, dactylitis, nail psoriasis, skin psoriasis and enthesitis domain. For axial involvement, magnetic resonance imaging (MRI) assessments were performed to provide potential involvement. Furthermore, clinical assessments included the number of tender joints (TJC) and swollen joints (SJC), patient-reported visual analog scale (VAS) scores for general health, pain, and disease activity, as well as the physician's VAS score for disease activity (MGA). Laboratory and clinimetric indices were also recorded, including C-reactive protein (CRP, mg/dl), Disease Activity in Psoriatic Arthritis Score-28 (DAPSA28)-CRP score, Health Assessment Questionnaire (HAQ), Disease Activity in Psoriatic Arthritis (DAPSA), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Psoriasis Area Severity Index (PASI), Nail Psoriasis Severity Index (NAPSI), Maastricht Ankylosing Spondylitis Enthesis Score (MASES), and Leeds Enthesitis Index (LEI). Moreover, additional data regarding comorbidities, and pharmacological therapy were also documented.

The primary outcome of this study was to investigate the prevalence characteristics of PsA in the Italian population, with a specific focus on gender distribution and clinical domain of disease presentation. The study aimed to assess and compare the prevalence of various PsA phenotypes, between gender groups and to enhance understanding of PsA presentation in Italy and support targeted management strategies by highlighting potential differences in disease characteristics between males and females.

Continuous variables were reported as mean ± standard deviation (SD) or median [interquartile range, (IQR)] depending on distribution. Categorical variables were reported as numbers and percentages. Differences between groups were assessed using the ANOVA or the independent t-test for continuous variables or by Pearson's χ² test for dichotomous variables. Probability (p) values < 0.05 were considered statistically significant. All analyses were performed using SPSS software 22.0 (Chicago, SPSS, Inc.).

Continuous variables were reported as mean ± standard deviation (SD) or median [interquartile range, (IQR)] depending on distribution. Categorical variables were reported as numbers and percentages. Differences between groups were assessed using the ANOVA or the independent t-test for continuous variables or by Pearson's χ² test for dichotomous variables. Probability (p) values < 0.05 were considered statistically significant. All analyses were performed using SPSS software 22.0 (Chicago, SPSS, Inc.).

The mean BMI in this cohort was notably similar between genders, though slightly higher in males (27.57 for males vs. 27.05 for females). However, obesity (defined as BMI ≥ 30) was observed in 31.46% of females compared to 24.32% of males, this distribution suggests potential gender-based differences in weight-related health impacts, possibly contributing to differential disease experiences.

Cardiovascular and metabolic comorbidities were common in this cohort, with 49.77% of males and 39.75% of females affected by at least one cardiometabolic condition (e.g., hypertension, diabetes, or dyslipidemia). Conversely, psychological comorbidities, including depression and anxiety, were more frequently reported among females (10.46%) than males (5.58%). These findings indicate a higher prevalence of psychological impacts in women with PsA, which may contribute to perceived disease burden. Inflammatory comorbidities, including inflammatory bowel disease (IBD) and uveitis, had similar rates between genders, with a prevalence of approximately 3% in both groups.

In terms of phenotype distribution: peripheral arthritis was the most prevalent form, observed in 91.2% of patients, with 42.7% showing an oligoarticular pattern and 48.5% a polyarticular pattern; enthesitis was present in 21.6% of patients; dactylitis was noted in 17.2%; axial involvement was observed in 15.9% and mutilans form was extremely rare in our cohort, occurring in only one patient (0.2%) (Figure 1). Most patients (62.6%) exhibited only one PsA phenotype at the time of assessment, while a smaller proportion (8.6%) presented with three distinct phenotypes, suggesting considerable heterogeneity in clinical presentation within this population.

Distinct gender-related differences were observed across phenotypes; while the overall prevalence of PsA is balanced between genders in our cohort (p = 0.385), distinct gender-based differences emerge when examining specific phenotypes. Men are significantly more likely to exhibit axial involvement (p = 0.012), whereas women show a higher prevalence of enthesitis (p = 0.044) (Figure 1).

Additionally, women reported higher scores for disease activity, reflected in the BASDAI, VAS, TJC, DAS28, and HAQ scores (all p < 0.05), indicating a higher burden of perceived disease activity. In contrast, men had significantly higher PASI scores (p < 0.001), suggesting more severe skin involvement. Further analysis of disease activity indices demonstrated a higher prevalence of elevated MASES scores among women (p = 0.022), specifically indicating more frequent entheseal involvement, although LEI scores did not show a significant gender difference (p > 0.05) (Figure 2).

These findings suggest that, despite similar overall prevalence, certain clinical manifestations of PsA vary by gender, underscoring the importance of gender-sensitive approaches in the management and assessment of PsA.

Overall, this cross-sectional analysis indicates that peripheral arthritis is the most prevalent PsA phenotype in this Italian cohort, with notable gender-specific variations in axial and enthesitic involvement. Additionally, the observed delays in diagnosis for a significant proportion of patients underscore the need for improved awareness and screening practices in PsA. The identified prevalence of smoking among male patients and the increased skin severity in males highlight potential areas for targeted interventions.

The main demographic, anthropometric and clinical characteristics of patients are summarized in Table 1. Significantly more men (86 patients [18, 94%]) were current or past smokers in confront with women.

This study provides valuable insights into the prevalence and characteristics of PsA phenotypes, comorbidities, and gender differences within an Italian cohort. However, several limitations should be considered when interpreting the findings. First, the absence of a non-PsA comparison group or general population data limits the ability to contextualize observed prevalence rates and demographic patterns beyond the PsA population studies. Additionally, the cross-sectional design restricts causal inferences and prevents tracking the evolution of disease phenotypes, comorbidities, and severity indicators over time; longitudinal data would be beneficial to assess the progression and long-term outcomes associated with these factors in PsA. Furthermore, the study cohort was sourced from a single geographic region, consequently affect the applicability of these results to different populations. Finally, missing data on important factors—like the time from symptom onset to diagnosis and the number of affected joints at disease start—was noted in over half of the patients. This limits our ability to fully understand early disease presentation and how delays in diagnosis might affect outcomes. Future research could address these gaps by using long-term studies, comparing with broader populations, and collecting more complete data to better understand PsA progression and management.