Cells of junctional EB patients (GABEB), compared to keratinocytes (HaCat) as well as cells of an EB simplex patient compared to primary skin fibroblasts as their respective non-EB reference cell lines, show similar properties in the differential accumulation of photosensitizers (Figures 15(a)–15(d)): PpIX formation is significantly reduced in GABEB and EBS-MD cells for both conditions (all: P ≤ 0.01, except for GABEB, 0.5 mM ALA and TNF-alpha, and EBS-MD, 1 mM ALA without TNF-alpha: both: P ≤ 0.05). This evidence concerns the gene TNF and epidermolysis bullosa.