The clinical utility of genetic risk variants in type 2 diabetes.

BACKGROUND: Type 2 diabetes is one of the first success stories in the application of genome-wide linkage and association studies to find genetic variants contributing to its risk. OBJECTIVE: Are the genetic markers found so far useful in predicting which individuals are more likely to develop type 2 diabetes? Can they find which patients with prediabetes are more likely to convert to type 2 diabetes and therefore may benefit the most from lifestyle or pharmacologic prevention strategies? METHODS: The literature pertaining to the discovery and replications of genes contributing to type 2 diabetes was focused on. RESULTS/CONCLUSION: Substantial risk for type 2 diabetes is represented by the top 8 genes, including TCF7L2, and in certain circumstances may be useful for prevention strategies targeted to those with highest risk.

Distinct clinical differences between HLA-Cw*0602 positive and negative psoriasis patients--an analysis of 1019 HLA-C- and HLA-B-typed patients.

A major susceptibility gene for psoriasis is located in the major histocompatibility complex class I region on chromosome 6 very close to the HLA-Cw6 gene. We collected a cohort of 1,019 patients with chronic plaque psoriasis. The patients were typed for HLA-C and HLA-B. A total of 654 (64.2%) were HLA-Cw*0602 positive but 365 (35.8%) carried other HLA-C alleles. We confirmed that HLA-Cw*0602 positive patients have younger age of onset (17.5 vs 24.3 years, P<10(-10)), higher incidence of guttate and the eruptive type of psoriasis (P<0.0001), more frequent exacerbations with throat infections (P=0.01), higher incidence of the Koebner's phenomenon (P=0.01), and more extensive disease (P=0.03). A striking new finding was a diverging pattern of disease severity in HLA-Cw*0602 positive and negative patients depending on the age of onset of the disease (P=0.0006). HLA-Cw*0602 positive women also had more frequent remissions during pregnancy (P<0.0001). All types of nail changes were, however, more common in the Cw*0602 negative patients (P=0.003) and they more often had multiple types of nail lesions (P<0.0001). The three ancestral haplotypes of Cw*0602 all conferred an increase in odds ratio but showed no difference in any of the clinical features studied. Our findings indicate that the genetic factor on chromosome 6 has a strong influence on the phenotype of the disease, and underline that differences in clinical features of psoriasis may be to a large extent genetically determined.

A genome wide linkage disequilibrium screen in Parkinson's disease.

Whole genome screening is increasingly used to identify genetic risk factors for complex diseases. In this study, a genome wide linkage disequilibrium (LD) screen was performed in a cohort of Parkinson's disease (PD) patients from the UK (n = 195) using pooled DNA to facilitate efficient genotyping of 5546 microsatellite markers. Allele frequencies were compared with those found in 2 previously typed disease free control populations, and the most interesting markers were selected for multiple repeat testing among the 3 pools. Markers were then individually genotyped in our original PD cohort and one of the original control groups, and independently in a second cohort of UK PD patients (n = 179), and additional controls. Using this 2-stage approach, we have been unable to find evidence for consistent association of any markers with sporadic PD. Subgroup analysis of the most promising marker shows some evidence that microsatellite marker D1S2886 is associated with familial forms of the disease.

The inheritance of hand osteoarthritis in Iceland.

OBJECTIVE: To assess the contribution of genetics to hand osteoarthritis (HOA) and its subsets in the Icelandic population. METHODS: A list of 2,919 HOA patients, constituting 1% of the Icelandic population, was compiled through nationwide sources. This patient list was cross-referenced with a comprehensive Icelandic genealogy database, enabling the use of algorithms to assess familiality of HOA. Two methods were used: the average pairwise kinship coefficient (KC) of the patients, and the relative risk (RR) of HOA in relatives of patients. In each case, the results were compared with 1,000 control sets of similar composition with regard to number, age, and sex, generated from the genealogy database. RESULTS: The KC for patients was significantly higher than for the control sets and was proportional to the degree of both interphalangeal (IP) and thumb base (first carpometacarpal [CMC] joint) involvement. The RR of HOA in sisters of women in the study was 2.0 (P < 0.001), while the RR in spouses was not significantly different from that in controls. The RR increased with the severity of the disease. Thus, sisters of women with severe IP HOA had an RR of 5.0 and sisters of those with severe first CMC involvement had an RR of 6.9. The increased risk also extended beyond the nuclear family, with significantly increased risk in cousins. CONCLUSION: Patients seeking medical services for HOA are more related to each other than matched controls, supporting the role of a genetic component in the disease. The genetic influence in both IP and first CMC HOA appears to be similar and increases with increasing severity of the disease.