BACKGROUND--Loricrin and involucrin are major precursor proteins to the cornified cell envelope expressed late in epidermal differentiation. Involucrin expression starts in the upper spinous layers in normal human epidermis and precedes loricrin expression, which is restricted to the granular layer. Subsequently, both proteins become cross-linked by the activity of transglutaminases TGK/E as major components of the cornified cell envelope by N epsilon-(gamma-glutamyl)lysine isopeptide bonds. In this study, three cases of lamellar ichthyosis were analyzed by immunohistologic study with antibodies to loricrin, involucrin, filaggrin, and transglutaminase TGK. OBSERVATIONS--A high expression of loricrin and involucrin with a peculiar and abnormal cytoplasmic staining concurred with a diminished cytoplasmic staining of transglutaminase TGK as assessed by antibodies B.C.1 and K.D.3. This pattern was absent in a collodion baby at birth but present 2 weeks later before a phenotype of lamellar ichthyosis appeared clinically. CONCLUSIONS--The results suggest that in our cases of lamellar ichthyosis, (1) disturbed membrane anchorage of transglutaminase TGK could alter loricrin and involucrin cross-linkage and the formation of the cornified cell envelope and that (2) immunohistologic study might serve as an early diagnostic and prognostic tool in the treatment of collodion babies.