Give a descriptive definition of ichthyosis.
Ichthyosis is a chronic, hypertrophic disease, characterized by dryness and scaliness of the skin, with a variable amount of papillary growth.
At what age is ichthyosis first observed?
It is first noticed in infancy or early childhood. In rare instances it is congenital (ichthyosis congenita), and in such cases it is usually severe, and of a grave type; the children are, as a rule, prematurely born, and frequently do not survive many days or weeks.
What extent of surface is involved?
Usually the whole surface, but it is most marked upon the extensor surfaces of the arms and legs, especially at the elbows and knees; the face and scalp, in mild cases, often remain free.
Name the two varieties of ichthyosis usually described.
Ichthyosis simplex and ichthyosis hystrix, terms commonly employed to designate the mild and severe forms respectively.
Describe the clinical appearances of ichthyosis.
The milder forms of the disease may be so slight as to give rise to simple dryness or harshness of the skin (xeroderma); but as commonly met with it is more developed, more or less marked scaliness in the form of thin or somewhat thick epidermal plates being present. The papillæ of the skin are often slightly hypertrophied. In slight cases the color of the scales is usually light and pearly; in the more marked examples it is dark gray, olive green or black.