M. Breitbart et al., A STUDY OF HUNGARIAN TWINS INVOLVING THE INFLUENCE OF GENETIC AND ENVIRONMENTAL-FACTORS ON BENIGN, MELANOCYTIC LESIONS, EJD. European journal of dermatology, 6(8), 1996, pp. 548-551
Multiple, benign, melanocytic nevi (MN) are a major risk factor for th
e development of cutaneous melanoma (CM). Sun exposure seems to increa
se the number of MN. This study was designed to determine the influenc
e of genetic and environmental factors on the development of MN. In No
vember 1992, moles were counted by a dermatologist in 20 monozygotic (
MZ) and 20 dizygotic (DZ) twins (Budapest, Hungary). All MN were recor
ded in a schematic figure and classified according to size, colour and
clinical criteria of ''atypia'' All subjects completed a standard que
stionnaire for sun exposure history. Standard intrapair correlations,
heritability and laterality correlations in MZ twins were calculated.
In MZ twins, the total nevus count correlated significantly (p < 0.005
). In contrast, there was only a significant correlation (p < 0.001) o
f MN greater than or equal to 2 mm with irregular borders in DZ twins.
The difference between standard intrapair correlations for MZ and DZ
twins was significant regarding the total nevus count for all MN (p <
0.05), total nevus count of ''small'' common MN (greater than or equal
to 2- < 5 mm) (p < 0.01), total nevus count for large (greater than o
r equal to 5 mm) MN (p < 0.01) and with irregular borders (p < 0.01).
Heritability was calculated at around 60%, thus 40% may be linked to e
nvironmental factors. Laterality correlations of MN counts on the arms
within and between monozygotic twins showed a positive trend regardin
g the influence of environmental factors. We could not find a signific
ant correlation between sun exposure history (childhood, adolescence)
and the number of pigmented lesions. In summary, there is a significan
t genetic influence on the incidence of benign melanocytic lesions; th
e association with environmental influences, especially ultraviolet ra
ys, requires further investigations.