The small proline rich protein (SPRR) gene family encodes a conserved group of cornified envelope (CE) proteins that are part of the human epidermal differentiation complex (EDC). The formation of the cornified envelope during the late stages of epidermal differentiation is essential for epidermal barrier function and protects the body against environmental attack and water loss. Additionally, the expression of SPRR proteins is linked to keratinocyte terminal differentiation. The SPRR gene family, namely comprises three subclasses of genes, SPRR1 (which contains two members), SPRR2 (which contains eight members) and SPRR3 (which contains one member). SPRR1 is found predominantly in follicular epidermis and oral mucosa, SPRR2 is expressed coherently in follicular and interfollicular epidermis and SPRR3 is absent in epidermis and strongly expressed in internal squamous.