John Updike is arguably one of the finest writers of contemporary America. His oeuvre is impressive. It is well-known that Updike had severe psoriasis and has written candidly on this subject. The first pathographical piece is relatively short and first appeared in the New Yorker magazine. “From The Journal of a Leper,” The New Yorker, July 19, 1976, p. 28. You can contact DJ Elpern for a PDF.
The second essay is easier to find. It is in the book "Self-Consciousness," Chapter ii. At War With My Skin. While both of these are worth reading, the second piece is more comprehensive.
Self-Consciousness can be purchased form Amazon or used from ABE Books
These are Updike's two essays on psoriasis that wer published in the New Yorker. They are available at Dermatology Central.
From the Journal of a Leper, The New Yorker, July 19, 1976, Pages 28 - 33
At War With My Skin, The New Yorker, September 2, 1985, Pages 39 - 57
New Yorker ABSTRACT: PERSONAL HISTORY telling how the writer has lived with psoriasis, a metabolic disorder that causes the epidermis, which normally replaces itself in the course of several days, to speed up the process and to produce excess skin cells. A tendency to it is inherited. The writer's mother had it and her mother had it. The disease favors the fair, the dry-skinned. It keeps you thinking. Strategies of concealment ramify and self-examination is endless. Because of his skin problem writer chose a profession that did not demand being presentable. He married young because he found a comely & gracious female who forgave him his skin. They moved to Ipswich, Mass, because the town had a great beach. Baking in the sun on the beach relieved the skin symptoms. Tells about their life in Ipswich. In August, to escape local biting flies they left and rented a house in Martha's Vineyard. In the winter he went to the Caribbean for the sun. Tells about these visits. In the fall of 1974 he left his wife and Ipswich. The next fall his skin was bad and he flew to St. Thomas but the sun did not help. At 42 he had worn out the sun At this time a few blocks from where he was living in Boston, dermatologists at Mass. Gen. Hospital were developing the PUVA program to treat psoriasis. lt was still in the experimental stage but he was accepted into the program. In a few months pills and artificial light did what salt water and sun could no longer do. His skin, was clear.