SKINIPEDIA - Skin Encyclopedia: Acne in Women (Genetics)
The Influence of Genetics and Environmental Factors in the Pathogenesis of Acne: A Twin Study of Acne in Women
by V Bataille*,†, H Snieder*, A J MacGregor*,‡, P Sasieni‡ and T D Spector*
- *Twin Research and Genetic Epidemiology Unit, St Thomas' Hospital, London, U.K.
- †Georgia Prevention Institute, Medical College of Georgia, Augusta, GA, U.S.A.
- ‡Department of Mathematics, Statistics and Epidemiology, Cancer Research U.K., London, U.K.
Correspondence: Dr Veronique Bataille MD PhD FRCP, Twin Research and Genetic Epidemiology Unit, St Thomas' Hospital, London SE1 7HT, U.K. Email: vbataille@twin-research.ac.uk
ABSTRACT
Acne is common and often leads to significant psychologic and physical morbidity. From clinical experience, acne appears to run in families; however, very few studies have investigated the genetic basis of this very common skin disease. A large twin study based on 458 pairs of monozygotic and 1099 pairs of dizygotic twins, all women with a mean age of 46 y was performed to investigate the relative contribution of genetic and environmental factors on the liability to acne. In addition, potential risk factors were assessed in twins with and without acne in a nested cross-sectional design. Fourteen percent of the twins reported a history of acne. Genetic modeling using acne scores showed that 81% (95% confidence interval 73–87%) of the variance of the disease was attributable to additive genetic effects. The remaining 19% was attributed to unique (i.e., unshared) environmental factors. Of the potential risk factors tested in 400 acne twins and 2414 unaffected twins, only apolipoprotein A1 serum levels were significantly lower in acne twins even after adjusting for age and weight. Family history of acne was also significantly associated with an increased risk. No significant differences were found between acne twins and nonacne twins for weight, body mass index, height, birth weight, hair thinning, reproductive factors as well as cholesterol, triglycerides, high-density lipoprotein, and glucose levels. The lower serum levels of apolipoprotein A1 in acne twins were also confirmed when analyzing acne discordant twin pairs. The evidence of a major genetic influence on acne should stimulate the search for potential genes that may lead to new therapeutic approaches.
Acne is one of the commonest skin diseases affecting between 40 and 50 million individuals in the U.S.A. alone with peak incidence in adolescence and mid-thirties in women (White, 1998). The expenditure for acne-prescribed drugs has been estimated at $4 billion worldwide. In 1992, in the U.K. alone there were about 3.5 million consultations for acne in the primary care sector (Simpson, 1994). The facial disfigurement caused by moderate to severe acne is important socially and economically as acne can cause difficulties in finding employment, low self-esteem, and depression (Cunliffe, 1986;Motley and Finlay, 1992;Gupta and Gupta, 1998). Despite the prevailing lay view that acne is caused by environmental factors, a U.K. study reported that cosmetics, prescribed drugs, and occupation were not associated with acne (Goulden et al, 1999a).
The pathogenesis of acne has not yet been elucidated but scant data from family studies suggest familial clustering (Goulden et al, 1999a,b). A few twin studies have previously been published investigating the genetics of acne. One study by Friedman reported high heritability estimates for acne in twins recruited from a large U.S. twin registry (Friedman, 1984). The diagnosis of acne was assessed from nonstandardized medical records retrieved from each twin within a pair but twins were not interviewed for the study. A preliminary report of a recent twin study of acne also showed high heritability estimates for acne in adolescent twins recruited from an Australian twin registry (Kirk et al, 2001). A twin study investigating sebum excretion in 40 pairs of adolescent acne twins found higher correlations in monozygotic vs dizygotic twins, but the numbers were small (Walton et al, 1988). The proportion of branched fatty acids in the sebaceous wax esters has also been reported to be more highly correlated in monozygotic twins compared with dizygotic twins (Stewart et al, 1986).
The combined twin and nested cross-sectional study reported here was set up to investigate potential environmental, hormonal, and metabolic as well as genetic risk factors for this disease, and also to quantify the relative contribution of genetic and environmental factors in acne causation using a large population-based sample of Caucasian female monozygotic and dizygotic twin pairs recruited from all over the U.K. Data on other common skin diseases, such as eczema and psoriasis were also collected but results on these diseases will be published separately. In view of links between acne and polycystic ovary syndrome (PCO) potential associations with hormone-related variables such as reproductive history, lipid metabolism [cholesterol, triglycerides, high-density lipoprotein, and apolipoprotein A1 (Apo A1)], and glucose levels were also investigated.