Keratins 5 and 14 are critical for cytoskeletal integrity, as shown by missense mutations in these genes, which cause the severe skin fragility disorder epidermolysis bullosa simplex (EBS). The complexity of the pathomechanisms in EBS is not fully understood and no effective management exists. In addition to fragility, EBS keratinocytes are characterized by aggregates of misfolded keratin. Here, we tested the chemical chaperone 4-phenylbutyrate (4-PBA) as a putative novel therapy, using keratinocytes from patients with severe generalized EBS due to distinct KRT5 and KRT14 mutations.