Genetic Analysis of Psoriasis in Iceland
Title: Genetics of psoriasis in Iceland: evidence
for linkage of subphenotypes to distinct Loci.
Authors: Karason A, et al.
Publication: J Invest Dermatol. 2005 Jun;124(6):1177-85.
The authors wanted to investigate the genetic basis for psoriasis.
They performed genome-wide scans for presence of genes that are
genetically linked to psoriasis in 238 Icelandic families with
874 patients. They also analyzed 1,000 patients with chronic plaque
psoriasis and documented several subphenotype or subforms of the
The authors found:
Gene Locations or Loci
The authors confirmed the linkage of psoriasis to MHC (major
histocompatibility protein), an immune system protein previously
thought to be involved in the development of psoriasis.
When the subforms of psoriasis were taken into consideration,
the likelihood of genetic linkage or LOD scores of the 16q and
4q increased dramatically. For example, when parental inheritance
was given more prominence, then the LOD score of the 16q is 5.7.
When age was given more weight during the analysis (i.e. disease
occurring at or older than 17 years of age), then the LOD score
of the 4q increased to 3.6. This genetic location was very close
to the previously found location that suggested signficant linkage
to psoriasis in the Chinese population and near suggestive linkage
to Caucasian population.
Another loci or genetic location called 10q had a LOD score of
3 when disease onset in the scalp was taken into account.
Editor’s Note: LOD score or Logarithmic Odds score
is a quantitative, logarithmic measurement to detect genetic linkage
(the higher it is, the more likely it is that the observed symptom
is genetically linked to that particular gene). For example, a
LOD score of 3 means that the likelihood of genetic linkage is
1000 times greater than no linkage.