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Biomedical subjects

J T Lear

Publications and source records attributed to J T Lear.

At least 19 recordsLinked to original sources
PubMed2006

Genetics and risk factors for basal cell carcinoma.

Nonmelanoma skin cancer (NMSC) is the commonest cancer in whites and its incidence is increasing worldwide. The prevalence of this cancer is predicted to equal that of all others combined and it was estimated that there were over 2 million cases diagnosed in the U.S.A. in 2004. Patients exhibit marked differences in clinical phenotype with variations in tumour numbers, rate of tumour accrual, site and histological subtype. Furthermore, patients are at increased risk of other cutaneous and noncutaneous cancers. The factors accounting for this variation are complex and still not completely understood. Clearly, ultraviolet light (UV) exposure is a major influence but its relationship to clinical phenotype is not yet clear. In addition, immunosuppression is a significant risk factor. Our group has identified high-risk groups for the development of further basal cell carcinoma (BCC), namely patients with truncal BCC and those presenting with tumour clusters. This presentation will concentrate on these clinical subgroups as well as immunosuppressed patients. These groups represent significant management challenges and are areas where novel, nonsurgical treatment options may make a significant clinical impact in patient care. The risk factors predisposing to these clinical phenotypes will be discussed, including genetic factors and UV exposure. Potential clinical applications, including predictive indices, will be considered.

Basal Cell Carcinoma↗
PubMed2006

Dermatological manifestations of Down's syndrome.

Down's syndrome (DS) is associated with rare dermatological disorders and increased frequency of some common dermatoses. Owing to advances in medical care and changes in attitude, the median age of death in this population has increased to 49 years, and the life expectancy of a 1-year-old person with DS today is more than 60 years and is likely to improve. With the increase in the number of individuals with DS in the population and an increased life span, dermatologists are more likely to encounter the wide spectrum of dermatological disorders that occurs in these patients. Furthermore, new reports of possible associations are frequent in the literature. The purpose of this article is to discuss the various dermatological conditions that affect DS individuals. A brief overview is given of the new information on genetics and the immunology of DS. We also discuss the molecular mechanisms of premature ageing, to which DS individuals are prone. We review the literature and discuss the known dermatological manifestations, concentrating on recent reports.

Adolescent↗
PubMed2006

Toxicodendron dermatitis in the UK.

BACKGROUND: We present two cases of Toxicodendron dermatitis, one acquired in the United States but presenting in the United Kingdom (UK), the other a recurrent dermatitis following importation of the plant to the UK. Poison ivy, poison oak and poison sumac are native to North America and belong to the genus Toxicodendron. This group of plants is of interest to the dermatologist because they contain a mixture of potent sensitisers which cause a severe allergic contact dermatitis. CONCLUSIONS: The dermatitis can present to the dermatologist in Europe after an individual has been in contact with the plant whilst visiting an endemic area. The plants have the potential to grow in Europe and it is therefore possible for an individual to be sensitised and subsequently to develop the rash without leaving the continent.

Adult↗
PubMed2005

Basal cell carcinoma: from host response and polymorphic variants to tumour suppressor genes.

The molecular factors and events that characterize susceptibility and outcome in cutaneous basal cell carcinoma (BCC) have been the focus of much research interest. As a result, we are beginning to understand the complex relationships between exposure to ultraviolet radiation (UVR), host response and the resulting damage to key genes that characterize these tumours. In this review, we will focus on genetic factors that influence susceptibility and outcome. While the search for susceptibility genes has generally resulted in the identification of low penetrance allelic variants, studies on modifier genes influencing outcome variables such as tumour number, age of onset and tumour subtype have identified factors with higher potential impact. Here we will briefly describe some recent work on the genetic basis of the immune response to UVR, the effect of UVR on the generation of reactive oxygen species and their detoxification, and the role of onco- and tumour suppressor genes. Areas for further research are highlighted, together with a consideration of possible applications in clinical practice.

Basal Cell Carcinoma↗
PubMed2004

Susceptibility to basal cell carcinoma: associations with PTCH polymorphisms.

Loss of function of the human patched gene (PTCH) is common and critical in basal cell carcinoma (BCC) development. Indirect evidence suggests polymorphism in PTCH mediates BCC risk. We studied 659 BCC cases and 300 controls to determine if exon 2(318), 3(429), 11(1552), 12(1665), 12(1686), 14(2199) and 23(3944) and intron 9(1336-135) and 15(2560+9)PTCH variants were sufficiently common for use in case-control studies, and if selected markers were associated with risk. Intron 15(2560+9) and exon 23(3944) variants were studied further. Their genotype frequencies were not significantly different in controls and cases, though frequency of the G(2560+9)-C(3944) haplotype was lower in all cases (odds ratio=0.44, p=0.009) and those stratified by BCC site and rate of development of further tumours. This association was not mediated by the extent of UVR exposure. We confirmed the robustness of these findings by showing these associations demonstrated similar odds ratios in two groups of randomly selected cases and controls, and using the false positive report probability (FPRP) approach described by Wacholder et al. (2004). The FPRP value (0.168) was in the noteworthy category. These data, showing for the first time that PTCH polymorphism mediates susceptibility, are compatible with reports showing that PTCH haploinsufficiency influences development of BCC precursor lesions.

Aged↗
PubMed2004

Occupational skin infections.

A number of skin infections may complicate different occupations depending on the working environment and level of exposure to a particular agent. These in turn may affect the productivity of an individual worker and ultimately the company as a whole. This review aims to highlight some common and important skin infections that may be acquired at work. Epidemiology, clinical features, diagnosis, treatment and prevention will be covered.

Dermatitis, Occupational↗
PubMed2001

Basal cell carcinoma follow-up practices by dermatologists: a national survey.

BACKGROUND: After treatment of a basal cell carcinoma (BCC) patients are at risk of recurrence of that BCC; also, patients who have had a primary BCC are those who have an increased risk of developing a subsequent primary BCC. However, long-term hospital-based follow-up of all patients would put large strains on the U.K. health service. OBJECTIVES: To investigate the follow-up intentions of U.K. dermatologists for well-defined facial BCC and to investigate the effect that variations in site and clinical indicators might have on those intentions. METHODS: A self-completion questionnaire relating to BCC follow-up sent to 388 dermatology consultants and associate specialists in the U.K. had a response rate of 68%. The effects of treatment modality, tumour site, histology, multiple lesions and various patient variables that might alter the likelihood of follow-up were examined. General views on the subject of BCC follow-up were sought. RESULTS: Twenty-seven per cent of respondents reported that they would not review further after excision of a 'well-defined' BCC from inside a central 'T' area on the face; 37% reported that they would review on one occasion; and 36% reported that they review more than once. CONCLUSIONS: While it is currently not feasible to follow-up all treated BCCs, a strategy to identify and monitor high-risk patients and a system to gather long-term outcome data prospectively are necessary aspects of a national health service. This study illustrates that the first issue is being addressed to some extent, but at the currently reported level of BCC follow-up in the U.K. there is little scope for collecting comprehensive long-term data on outcomes.

Attitude of Health Personnel↗
PubMed2001

Basal cell carcinomas: association of allelic variants with a high-risk subgroup of patients with the multiple presentation phenotype.

Previous studies have shown that patients who present at first or a later presentation with a cluster of new basal cell carcinoma (BCC) comprise a subgroup, termed multiple presentation phenotype (MPP), that is at increased risk of developing further lesions. In this study, we examined the hypothesis that patients who develop multiple clusters are a high-risk subgroup. We found, in a total group of 926 BCC patients, 32 patients with 2-5 BCC clusters (multiple cluster MPP) and 113 cases with only one cluster (single cluster MPP). Multiple cluster MPP cases had mean of 11.3 BCC compared with 3.7 in single cluster MPP cases during similar follow-up. Ultraviolet (UV) exposure in these groups was similar. We determined whether the multiple cluster MPP was associated with characteristics associated with sensitivity to UV or glutathione S-transferase (GST) GSTT1, GSTM1, cytochrome P450 (CYP) CYP2D6, tumour necrosis factor (TNF)-alpha and vitamin D receptor (VDR) genotypes previously associated with BCC presentational phenotypes. While the frequencies of blue eyes and male gender were greater in multiple cluster than single cluster cases, these differences were not significant. In multiple cluster cases, mean age at first presentation with single tumours occurred earlier and the frequencies of CYP2D6 extensive metabolizer (EM) (94.4%) and GSTT1 null (41.2%) were significantly greater (P = 0.028 and P = 0.004) than in single cluster cases (67.1% and 14.3%, respectively). The odds ratios for the individual associations of CYP2D6 EM and GSTT1 null with the multiple cluster MPP were relatively larger; 15.5 and 7.39, respectively. TNF-alpha and VDR genotypes were not associated with multiple cluster MPP. We propose that the MPP is not the consequence of excessive UV exposure but rather reflects the presence of a distinct BCC subgroup which is defined by combinations of risk genes.

Alleles↗
PubMed2001

Heavy cigarette smoking is strongly associated with rheumatoid arthritis (RA), particularly in patients without a family history of RA.

OBJECTIVES: To investigate the potential relation between cumulative exposure to cigarette smoking in patients with or without rheumatoid arthritis (RA) and a positive family history of the disease. METHODS: 239 outpatient based patients with RA were compared with 239 controls matched for age, sex, and social class. A detailed smoking history was recorded and expressed as pack years smoked. Conditional logistic regression was used to calculate the association between RA and pack years smoked. The patients with RA were also interviewed about a family history of disease and recorded as positive if a first or second degree relative had RA. The smoking history at the time of the study of the patients with RA with or without a family history of the disease was compared directly with that of their respective controls. Patients with RA with or without a family history of the disease were also compared retrospectively for current smoking at the time of disease onset. RESULTS: An increasing association between increased pack years smoked and RA was found. There was a striking association between heavy cigarette smoking and RA. A history for 41-50 pack years smoked was associated with RA (odds ratio (OR) 13.54, 95% confidence interval (95% CI) 2.89 to 63.38; p<0.001). The association between ever having smoked and RA was modest (OR 1.81, CI 1.22 to 2.19; p=0.002). Furthermore, cigarette smoking in the patients with RA without a positive family history of RA was more prevalent than in the patients with a positive family history of RA for ever having smoked (72% v 54%; p=0.006), the number of pack years smoked (median 25.0 v 4.0; p<0.001), and for smoking at the time of disease onset (58% v 39%; p=0.003). CONCLUSIONS: Heavy cigarette smoking, but not smoking itself, is strongly associated with RA requiring hospital follow up and is markedly more prevalent in patients with RA without a family history of RA.

Adult↗
PubMed2000

Basal cell carcinoma.

BACKGROUND: Basal cell carcinoma (BCC) is characterized by marked interpatient variation in tumor accrual. The authors previously reported that presentation with a cluster of BCC is associated with an inherited predisposition to develop many additional lesions suggesting clustering is a critical event. A cluster is defined as the presence of two or more new, primary BCCs, at initial or later presentation. METHODS: The authors recruited 927 cases and determined whether 1) clustering was an early or late event and 2) tumor accrual was altered after clustering. RESULTS: In the cases, 669 patients developed only 1 lesion, 112 patients presented more than once but with single lesions (single presentation phenotype[SPP]-more), 94 cases had a cluster at first presentation (multiple presentation phenotype [MPP]-cluster initial), and 52 cases first presented with 1 lesion but later had a cluster (MPP-cluster later). The authors found that 1) clustering occurred relatively late. The mean ages at first presentation with 1 BCC of the SPP-more (61.5 years) and MPP-cluster later patients (60.4 years) were similar although presentations with clusters in the MPP-cluster initial (67.6 years, P = 0.0002) and -cluster later cases (68.1 years, P = 0.002) occurred significantly later. 2) Clustering was associated with increased accrual. Thus, 26 patients (MPP-cluster later/a) in the MPP-cluster later group had a additional BCC postcluster. Mean accrual post-cluster (1.99 BCC/year) in these cases was significantly increased (P = 0.0001) compared with precluster accrual (0.39 BCC/year). CONCLUSIONS: The authors found that the formation of BCC clusters represents a critical event such that after a cluster presentation, tumor accrual is significantly increased. Cluster presentation is a relatively late event suggesting reduced effectiveness in immune surveillance.

Age Factors↗
PubMed2000

Detoxifying enzyme genotypes and susceptibility to cutaneous malignancy.

While ultraviolet (UV) exposure is thought to be a major risk factor for basal cell carcinoma (BCC) and squamous cell carcinoma, more recent research has focused on genetic factors predisposing to these cancers. UV constitutes an oxidative stress with generation of free radicals, leading to lipid and DNA damage and gene mutation. It could therefore be hypothesized that individual ability to deal with these products may be important in cutaneous carcinogenesis. It is clear from recent studies that polymorphisms in detoxifying enzyme genes are important in determining susceptibility to skin cancer. The magnitude of effect in BCC is similar to that seen with many other previously described risk factors. However, uncertainties exist regarding the phenotypic consequences of some of these polymorphisms and relevant substrates. This review describes the influence of polymorphisms in detoxifying enzymes in determining susceptibility to skin cancer (in particular to BCC) and give a brief overview of the biochemistry of the detoxification process.

Basal Cell Carcinoma↗
PubMed2000

Preliminary evidence of an association of tumour necrosis factor microsatellites with increased risk of multiple basal cell carcinomas.

Tumour necrosis factor alpha (TNF-alpha) appears important in ultraviolet-induced immunosuppression, suggesting that it is a susceptibility candidate for cutaneous basal cell carcinoma (BCC). We now describe data on the association between TNF microsatellite polymorphisms, first on susceptibility in 202 controls and 133 cases each having two to 30 BCCs, and secondly, within the cases, on BCC numbers. The data show that the proportions of individuals with TNF a1- and a7-containing genotypes were significantly different (P = 0. 0271, P = 0.0393, respectively) between cases and controls. Secondly, within the cases, TNF alleles d4 (P = 0.023) and d6 (P = 0.006) alone, and the TNF a2-b4-d5 haplotype (P = 0.007), were significantly associated with the number of BCC lesions. These preliminary data provide the first evidence that TNF microsatellite polymorphism may influence the pathogenesis of multiple BCC.

Alleles↗