Photoacoustic Imaging in Immune-Mediated Inflammatory Skin Diseases: Diagnostic and Therapeutic Applications

Background/Objectives: Immune-mediated inflammatory skin diseases (IMSDs), including psoriasis, atopic dermatitis, and systemic sclerosis, are chronic relapsing disorders that impose substantial physical, psychological, and economic burdens. Current assessment relies largely on subjective clinical scoring and conventional imaging modalities that provide limited functional information. This structured narrative review evaluates photoacoustic imaging (PAI) as a non-invasive optical-ultrasound technique for morphological and functional assessment in IMSDs. Methods: We searched PubMed studies published from January 2017 to December 2025 using terms related to photoacoustic imaging, optoacoustic mesoscopy, psoriasis, atopic dermatitis, systemic sclerosis, contact dermatitis, and immune-mediated inflammatory skin disease. Studies were narratively synthesized by disease, PAI modality, comparator, outcome, and translational limitation. Main Findings: PAI can map vascular and pigment-related optical absorption and estimate oxygenation, blood volume, and selected structural biomarkers. In psoriasis, atopic dermatitis, and systemic sclerosis, PAI-derived measures have been associated with clinical severity, subclinical vascular or epidermal changes, and treatment response. However, most available studies are small, single-center, heterogeneous, or based on prototype systems, and several biomarkers still require histopathological and external validation. Conclusions: Current evidence supports PAI as a feasible research and potential adjunctive assessment tool for IMSDs rather than an established replacement for standard clinical, histopathological, or imaging methods. Standardized protocols, validation across skin phototypes, cost-effective devices, and prospective multicenter studies are required before routine clinical adoption.