A number of COL7A1 mutations have now been reported in recessive dystrophic epidermolysis bullosa patients, and the analysis of phenotype-genotype correlations showed evidence for interfamilial and intrafamilial phenotypic variability, occurring for the same mutation. Collagenase and stromelysin activities have been found to be overexpressed in skin cultures of some recessive dystrophic epidermolysis bullosa patients, and tissue destruction in the disease process might result from an imbalance of metalloproteinases (MMP) over tissueinhibitor of metalloproteinases (TIMP). So we suspected that the phenotypic variability for the same mutation could be linked to other genetic or environmental factors, as a particular balance between MMP and TIMP. Organ cultures were performed using explants from the skin of three patients from the same family with recessive dystrophic epidermolysis bullosa to reveal and quantify the expression of MMP-1 (collagenase 1), MMP-2 and MMP-9 (gelatinases A and B), MMP-3 (stromelysin 1), TIMP-1, and TIMP-2, and to compare the results with those obtained with two human control skins, with the same experimental conditions. Increased amounts of all metalloproteinases investigated were observed in the skin of the three recessive dystrophic epidermolysis bullosa affected sibling brothers, both in lesioned and in apparently nonlesioned skin, compared with controls. The amounts of MMP-1, MMP-2, MMP-3, and MMP-9 increased particularly in the skin of the more clinically affected patient. Furthermore for this patient we evidenced higher amounts of MMP-1 and also a lower TIMP-1 amount in his unlesioned and lesioned skin compared with the other two affected patients and with healthy control donors. So we can suspect that recessive dystrophic epidermolysis bullosa phenotypic variability could be related to patients' collagenase activity heterogeneity, linked to imbalance between MMP-1 and TIMP-1.