JEB is an inherited blistering skin condition characterized by disadhesion of the basal keratinocytes from the basement membrane zone. Mutations in the components of the hemidesmosomes may be responsible for all forms of JEB. The largest group of mutations for this disease have been found in laminin-5, the primary component of the anchoring filaments that are part of the hemidesmosome complex. The binding of laminin-5 to specific cell surface receptors, α6β4 and α3β1, are therefore largely responsible for cell attachment. We made use of this fact to develop a cell attachment assay to use as a biological assay to predict patient prognosis on the basis of strength of cell attachment to extracellular matrix secreted by the patient cells. Patient cells or normal cells were allowed to secrete extracellular matrix proteins onto plastic microtiter plates for 24 hr, were lysed, and then normal cells were allowed to adhere to the resulting matrix. The binding strength of normal versus patient cell matrix are then compared. Antibodies versus laminin-5 were used to confirm that the binding is mediated primarily through laminin-5. We correlated the strength of attachment of normal keratinocytes to matrices secreted by JEB patients with laminin-5 defects possessing varying clinical phenotypes. We subtyped our patients clinically into three groups: infantile lethal, indeterminate, and adult forms of JEB. To compare patients within groups, severity and extent of blistering were used as clinical criteria. Attachment strength was quantitated by determining percentage cells remaining bound at a fixed centrifugal force (100g) for groups of varying clinical severity. Percentage cells bound was then plotted versus clinical severity to determine if a significant correlation existed. Percentage error was calculated by using standard error of the mean. Our findings show that decreased ability to attach correlates with severity of JEB. For example, matrix secreted by one of our more severe B9 patients binds only 5-10% cells as compared to the 50-60% seen with normal matrix. Another patient in the same group with much less severe clinical disease showed 20-30 % of the cells bound.