ANN ARBOR—Time and time again, Danish dermatologist Gunnar Lomholt came close to understanding how psoriasis is passed from one generation to the next. After years of study, however, he remained baffled by its complex patterns of inheritance. “It is hoped that another investigator may succeed,” he wrote in 1963, “when our knowledge of genetics has sufficiently increased.”

More than 30 years later, we’re getting there.

A collaboration between researchers at the University of Michigan Medical Center and the University of Kiel, Germany, has shed new light on the complex genetic roots of psoriasis—information which researchers believe will point the way to more effective treatments for the skin disease which afflicts 6 million Americans. The study’s findings are described in a paper published in the August issue of Human Molecular Genetics.

The research project, which involves more than 1,000 psoriasis patients or their relatives, also has provided evidence which may help explain why people with an inflammatory gastrointestinal disorder called Crohn’s Disease are seven times more likely than the general populace to suffer from psoriasis.

The U-M research for the first time has implicated a portion of Chromosome 16 in psoriasis. It also has confirmed three other regions already suspected of harboring psoriasis genes: portions of Chromosome 17, Chromosome 20 and Chromosome 6. The last of these is the home of the human leukocyte antigen (HLA) system, the genetic “turf” that controls organ transplant rejection and many other immune system functions.

The paper marks the first time that teams of scientists working independently have pinpointed the same genetic regions involved in making people vulnerable to psoriasis. Besides the U-M/Kiel team, the other groups involved are centered in London, England, and Dallas, Texas. Additional research is needed to isolate the specific genes involved and to ascertain the precise role each plays in triggering psoriasis, said Dr. James Elder, senior author of the study and an associate professor in the U-M Dermatology Department.

The discovery of a region of Chromosome 16 harboring a psoriasis gene may help explain the link between psoriasis and Crohn’s Disease, which has been traced by other researchers to the same location on Chromosome 16 as psoriasis, Elder said.

Psoriasis is characterized by red patches covered with a thick silvery scale. It typically affects skin on the elbows, knees and lower back, but 15 percent of psoriasis patients, about 1 million people in the United States alone, suffer from severe cases that can affect their ability to work, and 5 percent of psoriasis patients develop severe, deforming arthritis.

Management of psoriasis requires daily applications of medicated creams, treatment with ultraviolet light, or, in severe cases, treatment with immunosuppressive drugs and/or cancer chemotherapeutic agents. About 400 people a year die from complications of psoriasis or its treatment.

More information about this study and the genetics of psoriasis in general is available on the research team’s Web site at http://www.psoriasis.umich.edu. Psoriasis sufferers interested in participating in this study can call 1-800-356-2840 for more information.

More information: 

• James Elder
• Human Molecular Genetics
• U-M/Kiel team
• http://www.psoriasis.umich.edu