The dermatological spectrum of Turner syndrome

The Genes and Genetics of Malignant Melanoma

Background:

Population-based studies have identified several clinical variables associated with an increased risk of developing cutaneous melanoma that include phenotype, amount of and response to sun exposure, and family history. However, these observations are of limited relevance to clinical practice as the risk associated with each factor is individually modest and the characteristics of these variables lack precision when applied to a particular individual.

Objective:

To review the literature regarding recent advances made in the understanding of the genes and genetics of clinical variables associated with an increased risk of melanoma.

Conclusion:

Variants of the MC1R (melanocortin-1 receptor) have been identified as major determinants of high-risk phenotypes, such as red hair and pale skin, and the ability to tan in response to UV exposure. Several studies also suggest that such variants may increase melanoma risk independent of their contribution to phenotype. A strong genetic basis for both nevus density and size has been demonstrated and the link between nevi and the development of MM has become better defined. Finally, germline defects in several genes involved in cell cycle regulation, namely, p16 and CDK4, have been demonstrated in many familial melanoma kindreds. This progress has introduced the prospect of genetic testing as a means of identifying a limited number of high-risk individuals who can be targeted with regular screening and education regarding UV exposure and skin self-examination. Ultimately, through rational genetic therapy targeted to correcting the underlying molecular defect, altering the natural history of melanoma development may be possible.

Reduced sebum production in Turner syndrome: a study of twenty-two patients

Turner's syndrome (TS) is a genetic disorder caused by numeric and/or structural abnormalities of the X chromosome. In a previous study it was observed that acne is less frequent in TS than in the general population. Since the onset of acne in pre-pubertal or pubertal age is related to sebum production, this study evaluates sebum secretion in TS patients, comparing the results with those of a control group of age-matched healthy female subjects. A total of 22 patients affected by TS (mean age 26.56±7.89 years) and a control group of 23 age-matched healthy females were studied. Sebum production was measured using a Sebumeter SM810. Mean sebum secretion in TS subjects was significantly lower than in the control group (81.35±66.44 UA vs 147.09±33.62 UA, p<0.001) and this significant difference was found in every facial zone. The reduction of sebum secretion may explain, using a simple and non-invasive method, the absence or the low incidence of acne in TS patients.

Halo nevus, rather than vitiligo, is a typical dermatologic finding of Turner's syndrome: Clinical, genetic, and immunogenetic study in 72 patients

Turner's syndrome (TS) is a genetic disorder caused by numeric and/or structural abnormalities of the X chromosome; it is characterized by short stature, gonadal dysgenesis, and frequently by webbed neck, cubitus valgus, and lymphedema at birth. TS has been associated with several cutaneous abnormalities including an increased frequency of pigmented nevi, but few reports consider nevi in detail. Halo nevus (HN) is clinically defined as a melanocytic nevus surrounded by a halo of depigmentation. Vitiligo, a dermatologic disorder characterized by the presence of depigmented patches on the skin, has been described in the list of cutaneous findings associated with TS. The aim of this study was to determine the prevalence of HN and vitiligo in TS and to evaluate if a correlation between major histocompatibility complex genes, karyotype, autoimmunity, therapies, and the presence of HN exists. Of the 72 patients with TS examined, 13 had HN, a prevalence of 18.05%, which was significantly higher than in our control group (1%; P=.000001). On the contrary, only 2 patients with TS (2.77%, P=not significant) had vitiligo. By comparing the distribution of HLA class I alleles between patients with TS who did (13 of 72) and did not (59 of 72) have HN, we observed a significantly higher frequency of HLA-Cw6 in patients with TS and HN than in those without HN (26.92% vs 6.78%, respectively; P=.0067; odds ratio=5.06). The study of HLA class II genomic polymorphisms showed that the DRB1(*)0701 and DQB1*02 alleles for patients with TS and HN were overrepresented when compared with those without HN (34.61% vs 11.86%, respectively, P=.0078, odds ratio=3.93; and 34.61% vs 19.49%, respectively, P=.1386, odds ratio=2.19). In conclusion, this study is the first to demonstrate an increased prevalence of HN for patients with TS. Furthermore, the data suggest that a HN putative susceptibility gene in TS is located close to the HLA-C locus.

Turner's syndrome in dermatology

Turner's syndrome (TS) is a common genetic disorder of girls and women, for which the defining clinical triad is short stature, impaired sexual development, and infertility. Although classically known as monosomy X, genetic heterogeneity is frequent in TS, with mosaicism conferring a survival advantage. Several genetic loci have been implicated in TS including the short stature homeobox gene. TS effects many organs, with cutaneous stigmata providing critical clues for early detection of TS. The presence of lymphedema and its cutaneous sequelae are predictive of other systemic disorders, such as cardiac disease. Although an increased number of benign nevi have been reported in TS, the decreased melanoma rate in this population suggests some protective factor is active. Keloids were thought to be prevalent in TS, but recent data suggest otherwise. Autoimmune diseases are common in TS, with a possible increased prevalence of alopecia areata and vitiligo. The following review discusses new insights into the genetics and pathogenesis of this complex disorder, summarizes the major systemic effects, and reviews skin manifestations of TS and their implications.

Influence of genetic and environmental factors on melanocytic naevi: a lesson from Turner's syndrome

Females with Turner syndrome (TS) are alleged to have increased numbers of melanocytic naevi. Although a high count of acquired melanocytic naevi (AMN) is one of the major risk factors for melanoma, this malignancy has been reported only rarely in patients with TS. The purpose of this study was to explore the effects of environmental and genetic factors on AMN count and density in TS. AMN count and density in 24 patients with TS treated with growth hormone (GH). 24 GH-treated females with GH deficiency (GHD) and 24 normal females were compared in a cross-sectional study. The average AMN density in TS was 50 naevi/m2 as compared with 18 naevi/m2 in the GHD group and 24 naevi/m2 in normal controls (P = 0.001 and P = 0.004, respectively). Duration of GH therapy did not correlate with AMN count (P = 0.44) or AMN density (P = 0.81). The pattern of distribution of naevi between constantly exposed, intermittently exposed and unexposed skin was similar in all groups. Sun exposure was the major factor that affected the regional AMN densities in the control groups, but not in the TS group. The findings of our study indicate that the effects of environmental factors on AMN count and density may vary among genetically different populations. A review of the literature suggested that melanoma is no more prevalent in TS than in the general population.

Naevocyte triggering by recombinant human growth hormone

The influence of growth hormone and insulin-like growth factor I on human melanocytes is being increasingly recognized. Clinical evidence has shown that when recombinant human growth hormone (hGH) is administered to children of short stature, the growth of melanocytic naevi is boosted. This study was conducted on 56 hGH-triggered naevi and nine similar lesions excised before or after hGH therapy for hypopituitarism and Turner's syndrome. A series of 40 naevi excised from age-matched healthy children served as controls. Atypicality of naevocytes was investigated using image analysis, AgNOR counts, immunohistochemistry (HMB-45, NKI-C3, Ki-67, anti-bcl-2-oncoprotein), and DNA flow cytometry. The data associate hGH treatment with anisokaryosis and increased AgNOR and Ki-67 counts in naevocytes. The same cells also show abnormal patterns of HMB-45 immunolabelling. These indications of naevocyte activation were not suggestive of malignant transformation. hGH-triggered melanocytomas should be added to the list of atypical melanocytic naevi. The long-term evolution of these lesions remains unknown and the potential risk of malignant transformation awaits careful evaluation.