Filaggrin and filaggrin-2 protein expression is reduced in lesional MF skin, TEWL is increased, and epidermal immune infiltrates correlate with the reduced expression levels. (A) Lesional and nonlesional (NL) skin biopsies obtained from a patient with MF (MF1), and a healthy donor, were stained for hematoxylin and eosin stain (H&E), filaggrin, and filaggrin-2. The arrowheads highlight areas of deficient filaggrin and filaggrin-2 protein expression. (B) TEWL (g/m² per hour) measurements were performed for anatomically matched lesional and nonlesional sites in 12 patients with patches, plaques, or advanced lesions (tumor/erythroderma) (left). Some patients had multiple lesions that were analyzed. Lesional skin biopsies from 3 patients with MF and 1 with Sézary syndrome (MF5, MF6, MF7, and SS1) and nonlesional skin biopsy from patient MF5 were stained for filaggrin (right). Micrograph close-up for patient MF6 illustrates areas that lack filaggrin expression. ΔTEWL values (subtracting nonlesional from lesional values) were given for each of the patients. (C) Lesional skin site biopsies obtained from 3 patients with MF (MF8, MF9, and MF10) and a biopsy from a healthy donor were stained for filaggrin, filaggrin-2, and TOX. Areas of positive TOX staining in the epidermis/dermis are highlighted by black circles. Images are scanned by the Zeiss Axio Scan.Z1 with original magnification ×20 for all panels. Scale bars; 200 μm. Close up; 300%.