Sodium in the skin: a summary of the physiology and a scoping review of disease associations.

This article focuses on the emerging role of skin sodium in regulating total body sodium and its associations with various disease states. Recent research using sodium (^23Na) magnetic resonance imaging (MRI) has shown that skin sodium concentration is elevated in patients with cardiometabolic conditions (such as hypertension, heart failure, type 2 diabetes mellitus, and chronic kidney disease), autoimmune diseases (including multiple sclerosis and systemic sclerosis), and dermatological disorders (such as atopic dermatitis, psoriasis, and lipoedema). Skin sodium may contribute to physiological processes like osmoregulation and immune defense but can also promote immune dysregulation through proinflammatory pathways. Factors influencing skin sodium levels include age, sex, dietary sodium intake, pharmacological treatments (e.g., diuretics and sodium-glucose co-transporter-2 inhibitors), and haemodialysis, though findings on some interventions remain inconsistent. The article highlights the potential of skin sodium as a biomarker for immune-mediated diseases and a target for therapeutic strategies, while noting the need for further research to clarify its clinical significance.