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pathogenesis:
| • | abnormal transglutaminase gene (?) |
| • | accelerated rate of epidermal turnover with proliferation |
| • | the corneocyte has a highly insoluble cornified envelope its formation represents an expression of terminal differentiation of the keratinocyte within the plasma membrane, formed by the cross-linking of the soluble protein precursor involucrin (Greek = envelope) |
| • | envelope precursors (e.g. involucrin, loricrin) are synthesized late in stratification and then cross-linked by the action of transglutaminase enzymes, which are synthesized in the granular layer |
| • | major cell envelope constituents = involucrin, filaggrin and loricrin |
| • | defect in ichthyosis vulgaris – filaggrin |
| • | defect in Vohlwinkel’s syndrome – loricrin |
| • | defect in lamellar ichthyosis - transglutaminase |
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clinical:
| • | newborn – collodion baby |
| • | child/adult – large plate-like scales |
| • | flexural involvement is characteristic and distinguishes lamellar from the more common ichthyosis vulgaris |
| • | decreased sweating with heat intolerance |
| • | ddx: CIE, Netherton syndrome, trichothiodystrophy |
see Ichthyoses
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