Disorders of cornification that are characterized by visible scaling and/or hyperkeratosis of most or all of the skin. Inherited ichthyoses, defined as the generalized form of Mendelian disorders of cornification, affect most or all of the skin. This etiologically and phenotypically heterogenous group of conditions is caused by mutations in various different genes important for keratinocyte differentiation and epidermal barrier function. Acquired forms of ichthyosis can be observed with certain autoimmune, inflammatory, metabolic, endocrine, or infectious diseases or with malignancies. [ http://www.ncbi.nlm.nih.gov/pubmed/22739337 ]