CK1 (Cytokeratin-1) is an intermediate filament protein. CK1 regulates the activity of kinases such as PKC and SRC via binding to integrin beta-1 (ITB1) and the receptor of activated protein kinase C (RACK1/GNB2L1). Defects in CK1 are a cause of bullous congenital ichthyosiform erythroderma, also known as epidermolytic hyperkeratosis (EHK) or bullous erythroderma ichthyosiformis congenita of Brocq. BCIE is an autosomal dominant skin disorder characterized by widespread blistering and an ichthyotic erythroderma at birth that persists into adulthood.