The serine protease inhibitor of Kazal-type 9 (SPINK9) is expressed in lichen simplex chronicus, actinic keratosis and squamous cell carcinoma.

The serine protease inhibitor of Kazal-type (SPINK) 9 was reported to be exclusively expressed in palmoplantar skin. SPINK9 is a specific inhibitor of the serine protease kallikrein-related peptidase 5 (KLK5), which contributes to the desquamation process of the stratum corneum. Herein, we demonstrated that SPINK9 is also expressed in lichen simplex chronicus. Moreover, we observed expression of SPINK9 in 51 % of lesions of actinic keratosis and squamous cell carcinoma. In conclusion, we demonstrate that SPINK9 is not only expressed in healthy palmoplantar skin, but also in dermatologic disorders like lichen simplex chronicus, actinic keratosis and squamous cell carcinoma.