SPRR2E (small proline rich protein 2E) is a keratinocyte-specific structural protein that functions as a cross-linked envelope component of the epidermis. Synthesized initially in the cytosol, SPRR2E becomes covalently cross-linked to membrane proteins via transglutaminase, contributing to the formation of the insoluble cornified envelope beneath the plasma membrane 1. This protein plays a critical role in keratinocyte differentiation and keratinization, as evidenced by its significant enrichment in pathways related to epidermal development and cell differentiation 1. Clinically, SPRR2E expression is dysregulated across multiple pathological conditions. In diabetic foot ulcers, SPRR2E is significantly downregulated compared to normal skin, suggesting its reduced expression impedes wound healing and ulcer resolution 1. Similarly, SPRR2E expression is altered in inflammatory skin conditions, including psoriasis, where it correlates with genes participating in cell proliferation and epidermal differentiation 2. In malignancies, SPRR2E serves as a prognostic marker in cutaneous melanoma 3, oral squamous cell carcinoma 4, lung squamous carcinoma 5, and eosinophilic esophagitis 6, where its expression patterns contribute to cancer-associated pathways and patient survival prediction. These findings establish SPRR2E as a key biomarker linking epidermal homeostasis to disease pathogenesis.