"Special population" implicates environmental vitiligo triggers.

Amajor recessive gene appears to govern susceptibility to vitiligo, but actual disease on set depends on environmental triggers, researchers reported.

Dr. Stanca A. Birlea and associates at the University of Colorado, Denver, studied the epidemiology and genetics of vitiligo in a geographically isolated community in the mountains of northern Romania that has had "essentially no immigration or emigration" since its founding in the 16th century.

This community of 1,673 people included 51 with vitiligo, for a prevalence of approximately 3%. This is approximately 20 times higher than the prevalence of vitiligo in surrounding villages and is 7-20 times higher than various populations reported in the literature, the investigators said (Arch. Dermatol. 144:310-6).

The subjects' clinical characteristics were similar to those reported elsewhere, and the most frequent pattern was generalized disease involving less than 25% of the skin surface. "Fractional skin surface involvement was directly correlated with disease duration in most patients," Dr. Birlea and associates said.

Also as reported in other locations, the frequencies of several autoimmune diseases--thyroid disease, adult-onset type 1 diabetes mellitus, and rheumatoid arthritis--were highly elevated in these vitiligo patients and their first-degree relatives. This suggests "the community segregates genetic risk factors that contribute to an autoimmune diathesis that includes vitiligo" and these other disorders, the researchers said.

Interestingly, the mean age of onset of vitiligo was 36 years, which is significantly later than the usual age of onset (24 years) reported in the literature, the researchers said.

Genetic analysis suggested that there is "a single major recessive locus with incomplete penetrance, consistent with reduced causal genetic heterogeneity in this isolated and relatively inbred population, although this analysis does not exclude a more complex causation," they noted.

Heritability analysis indicated that the age of onset in this community was determined "almost completely by nongenetic environmental factors" that have not yet been identified, Dr. Birlea and associates said.

This study population offers the opportunity to map and identify vitiligo genes. Any variations found here are of particular importance to this "special population" but also are likely to be involved in disease susceptibility in the broader population. Identifying the involved genes will lead to understanding of key disease processes and pathways, which should in turn provide therapeutic targets, the investigators said.

BY MARY ANN MOON

Contributing Writer