Total Calcium and Albumin Are Decreased in the Deeper Epidermis of Patients with Chronic Kidney Disease-Associated Pruritus

Abstract

Background/Aims: In our earlier studies, we reported high concentrations of intra- and extracellular calcium ions (Ca²⁺) in the deeper epidermis of patients with chronic kidney disease (CKD) and associated pruritus. To determine the cause of this phenomenon, we measured total calcium (TCa) concentrations in the deeper epidermis and performed immunostaining of epidermal albumin, which binds to Ca²⁺. Methods: This study included 45 patients with CKD-stage 5, which was defined as severely reduced kidney function (i.e., estimated glomerular filtration rate less than 15 mL/min or on dialysis). Subjects were divided into the pruritus group, consisting of patients with mild, moderate, or severe uremic pruritus, and the non-pruritus group, consisting of patients with no or slight pruritus. The particle-induced X-ray emission method was used to measure elements including TCa. Furthermore, we have immunostained epidermal albumin using anti-albumin antibodies and compared the results in the pruritus and non-pruritus groups. Results: The TCa concentration in the spinous layer of patients with CKD with CKD-associated pruritus was lower than in patients with CKD without pruritus (median [range], 395 [235-1,063] vs. 476 [342-1,243] μg/g). The intensity of epidermal albumin expression in the spinous layer was weaker in patients with CKD with CKD-associated pruritus than in those without. Conclusion: Patients with CKD with CKD-associated pruritus demonstrated higher Ca²⁺ concentrations but lower TCa concentrations than patients without CKD-associated pruritus. This could be in part due to low concentrations of epidermal albumin, which binds to Ca²⁺, in those with CKD-associated pruritus. These results clarify the pathophysiology of CKD-associated pruritus, providing a valuable foundation for the future development of treatments for this condition.