In the past several years, the underlying gene defects for many types of hereditary palmoplantar keratodermas have been defined. The involved genes encode intracellular structural proteins, desmosomal proteins, gap junction component, and enzymes. Mapping of gene mutations that underlie palmoplantar. keratodermas provide better understanding of the functional significance of the proteins involved in terminal keratinocytes differentiation. As we gain understanding of the specific functional consequence of each mutation on the molecular level, we will better understand the pathophysiology of hereditary palmoplantar keratodermas