PSAPL1 (prosaposin like 1) is a cytosolic protein implicated in lipid metabolism and immune regulation. Based on functional annotations, PSAPL1 may activate lysosomal degradation of sphingolipids and participates in adenylate cyclase-inhibiting G protein-coupled receptor signaling, with potential roles in prostate gland development and epithelial cell differentiation. At the disease level, PSAPL1 emerges as a genetically causal factor in multiple pathophysiologies. Mendelian randomization analysis identified PSAPL1 as a causal protein for hyperthyroidism 1, suggesting therapeutic potential in thyroid disorders. In gastric cancer, PSAPL1 was identified as one of three T2DM-related genes in a prognostic risk model, where high expression associated with worse overall survival (AUC: 0.786-0.757) 2. PSAPL1 also serves as a candidate diagnostic biomarker for gastric cancer and participates in immune cell infiltration regulation through the H19/miR-378a-5p/SERPINH1 ceRNA network 3. In dermatological conditions, PSAPL1 variants were significantly enriched in Japanese patients with face-and-neck atopic dermatitis, suggesting involvement in innate immune pathways 4. In breast cancer, PSAPL1 was among eight genes associated with Nottingham grade and its morphological components, relating to cellular proliferation and differentiation 5. Finally, PSAPL1 was identified as a protein potentially contributing to maintaining the non-lesional state in psoriatic skin 6.