Characteristics of Skin Surface Morphology and Transepidermal Water Loss in Clinically Normal‐Appearing Skin of Patients with Atopic Dermatitis: A Video‐Microscopy Study

In patients with atopic dermatitis (AD), it is debatable whether clinically normal‐appearing skin is equal to non‐atopic normal skin. The aim of this study was to quantitatively evaluate the characteristics of normal‐appearing skin of AD. We examined the value of skin surface morphological changes using a new, simple, computer‐assisted method with a video microscope. We also investigated the physiological function as represented by transepidermal water loss (TEWL) levels in 44 patients with AD and 15 normal controls. The morphological changes were represented by a variation coefficient score that reflected the irregularity of skin ridges, named the surface irregularity index (SII). There were significant differences between the normal‐appearing skin of AD and non‐atopic normal skin in both SII (P<0.001) and in TEWL (P<0.01). Especially for the SII, there were significant differences between AD subgroups subdivided by peripheral blood eosinophil count (Eo), serum lactate dehydrogenase level, and clinical score. TEWL values were significantly higher in the high‐Eo AD group (n=15) than in the low‐Eo AD group (n=29) (P<0.05). These findings indicate that clinically normal‐appearing skin of AD patients with high disease activity differs from non‐atopic normal skin in both surface morphology and physiology and that these changes reflect the current disease activity.