Woman with ichthyosis. Ichthyosis (plural ichthyoses) is a heterogeneous family of at least 28, generalized, mostly genetic skin disorders. All types of ichthyosis have dry, thickened, scaly or flaky skin. In many types there is cracked skin, which is said to resemble the scales on a fish; the word ichthyosis comes from the Ancient Greek meaning "fish." Photograph taken by George Henry Fox, 1886.