Characterization of Epidermal Function in Individuals with Primary Cutaneous Amyloidosis

Purpose: To compare epidermal biophysical properties, indicators of epidermal function, in individuals with and without primary cutaneous amyloidosis (PCA). Patients and Methods: This study incorporated 189 patients with PCA and 166 healthy individuals. The GPSkin Barrier was employed to measure transepidermal water loss (TEWL) rates and hydration levels of the stratum corneum. The Sebumeter and the Skin pH Meter were utilized to determine the skin surface’s sebum content and pH, respectively. The severity of pruritus in participants was evaluated using the visual analog scale (VAS). Results: Compared to the control group without PCA, individuals with PCA displayed a notable increase in skin surface pH and TEWL and a decrease in the hydration levels of the stratum corneum ( p < 0.0001 for all parameters). Additionally, the sebum content was markedly lower in those with PCA than in the controls ( p < 0.0001). Of particular note, both TEWL and skin surface pH at the lesion sites on the back and the shin were more elevated in lichenoid amyloidosis (LA) and in macular amyloidosis (MA), whereas hydration levels of the stratum corneum and sebum levels were diminished in LA compared to MA ( p < 0.05). In conclusion, both hydration levels of the stratum corneum and sebum content exhibited an inverse relationship with pruritus severity, whereas TEWL and skin surface pH demonstrated a positive correlation with pruritus intensity. Conclusion: The function of the epidermis is compromised in individuals diagnosed with PCA. However, the mechanisms underlying these changes await further investigation. Keywords: cutaneous amyloidosis, epidermis, biophysical properties, pruritus