Exploratory MRI and Clinical Marker Analysis of Pustulotic Arthro-Osteitis Disease Activity From a Phase 3 Brodalumab...

Pustulotic arthro-osteitis (PAO) is a clinically important osteoarticular comorbidity affecting approximately 9%-28% of patients with palmoplantar pustulosis (PPP), yet early recognition and standardized activity assessment remain challenging, particularly in routine dermatology practice. This exploratory analysis evaluated patients with PAO to identify potential indicators of disease activity. A magnetic resonance imaging (MRI)-based scoring system for the anterior chest wall (ACW) in patients with PAO was developed. This post hoc analysis used data from the PAO subgroup of patients with PPP enrolled in a previous phase 3 trial. Correlations were assessed between clinical indicators-Ankylosing Spondylitis Disease Activity Score, Assessment of SpondyloArthritis international Society Health Index score, physicians' Numeric Rating Scale-PAO (NRS-PAO) activity score, and patients' NRS-PAO pain score-and MRI indicators, including active lesions such as bone marrow edema extent and intensity, and structural lesions in the ACW, spine, and sacroiliac joints (Spondyloarthritis Research Consortium of Canada [SPARCC] score); the correlations between MRI indicators and plain radiographic indicators were also evaluated. Of 20 included patients (mean age: 56.6 years), the majority were female. MRI examinations detected bone marrow edema in all patients. None of the clinical indicators showed a clear association with MRI indicators. There was no clear association between radiographic indicators and the bone marrow edema extent or intensity scores of lesions in the ACW. The spine SPARCC score was positively correlated with the osteosclerosis score of the ACW (|r| = 0.70; p = 0.0218) and the modified Stoke Ankylosing Spondylitis Spinal Score of the spine (|r| = 0.93; p < 0.001). The MRI-based ACW scoring system may provide a feasible method to standardize disease activity assessment in PAO in clinical practice. Further external validation is warranted, and additional clinical indicators are needed to predict disease activity. Trial Registration: NCT04061252, UMIN000055398.