Expression of stratum corneum chymotryptic enzyme in ichthyoses and squamoproliferative processes

Stratum corneum chymotryptic enzyme (SCCE) is a serine protease, which is thought to play a role in the desquamation of skin via the proteolysis of desmosomes in the stratum corneum. The objective of this study was to investigate the expression of SCCE in ichthyoses and squamoproliferative processes, conditions in which the shedding and replacement of epidermal cells is disrupted.

Tissue samples from cases of Netherton's syndrome, congenital ichthyosiform erythroderma, ichthyosis vulgaris, actinic keratosis, squamous cell carcinoma in situ, and invasive squamous cell carcinoma were examined for expression of SCCE using immunohistochemistry.

The slides were qualitatively analyzed for the expression of SCCE by a certified dermatopathologist.

In all disease states, we found that the expression of SCCE was absent in areas of parakeratotic stratum corneum of normal thickness. In areas of mixed orthokeratosis and parakeratosis where the stratum corneum was greatly thickened as might correspond clinically to a cutaneous horn, SCCE staining was either absent or focally aggregated without regard to orthokeratosis or parakeratosis. Of note, complete absence of SCCE expression was not observed in any of the cases of ichthyosis examined, nor was there increased expression of SCCE in the atypical cells of the squamoproliferative disorders.

These results suggest that SCCE is abnormally expressed in skin where epidermal cell kinetics are disrupted due to inherited and acquired defects. Further investigation is needed to determine causality between the abnormal expression of SCCE and the altered cell kinetics in these diseases.