Collodion baby: ultrastructure and distribution of cornified cell envelope proteins and keratins.

The pathogenesis of 'collodion baby' has not been clarified yet, and this descriptive term is thought to include several heterogeneous conditions. We report a collodion baby whose clinical features had changed to those of lamellar ichthyosis (LI) as the patient got older. By electron microscopy, skin specimens at 3 days of age revealed the presence of lipid inclusions within the cornified cells, abnormal lamellar granules in the granular layer keratinocytes and a lack of extracellular lamellar structure between the first cornified cell and the granular cell though the cornified cell envelope appeared to be normally formed. Immunohistochemical labeling showed normal distribution of keratins 1, 5, 10, 14, filaggrin/profilaggrin and cornified cell envelope proteins (involucrin, small proline-rich proteins and loricrin). These observations suggested that a collodion baby might have a normal cornified cell envelope and show morphologic changes similar to those of harlequin ichthyosis at birth, even though its underlying disorder is LI.