Epidermolytic hyperkeratosis (EH) is a distinctive histologic expression of an epithelial pathologic process. The characteristic histopathologic features appear in a variety of acquired and congenital skin lesions. They range from focal EH confined to a single rete ridge, that is clinically unapparent, to widespread EH that is manifested clinically as bullous congenital ichthyosiform erythroderma. Microscopic examination enables detection of EH beneath an array of clinical masquerades.
Ackerman AB. Histopathologic Concept of Epidermolytic Hyperkeratosis. Arch Dermatol. 1970;102(3):253-259. doi:10.1001/archderm.1970.04000090015003