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Disease-causing variants in key immune homeostasis genes can lead to monogenic autoimmune diabetes. Some individuals carrying disease-causing variants do not develop autoimmune diabetes, even though they develop another autoimmune disease. We aimed to determine whether type 1 diabetes polygenic risk contributes to phenotypic presentation in monogenic autoimmune diabetes. We used a 67 single nucleotide polymorphism type 1 diabetes genetic risk score (T1D-GRS) to determine polygenic risk in 62 individuals with monogenic autoimmune diabetes and 180 control individuals with nonautoimmune neonatal diabetes (NDM). We used population-based control participants (n = 10,405) and individuals with type 1 diabetes (n = 285) as a comparator. Individuals with monogenic autoimmune diabetes had higher T1D-GRSs compared with individuals with nonautoimmune NDM (mean 11.3 vs. 9.8; P = 1.7 × 10−5) and controls (mean 10.3; P = 7.5 × 10−6), but the levels were markedly lower than those for individuals with type 1 diabetes (14.9; P = 3.3 × 10−21). These differences were explained by individuals with monogenic autoimmune diabetes having higher class II HLA genetic risk, specifically from the DRB1* 03:01 -DQA1 *05:01 -DQB1 *02:01 haplotype (DR3-DQ2) (P < 0.01). In the presence of monogenic autoimmunity, the polygenic class II HLA susceptibility contributes to development of autoimmune diabetes. This suggests a role of class II HLA in targeting the dysregulated immune response toward the β-cell. Article Highlights: There is variability in early-onset autoimmune diabetes presentation in individuals with monogenic autoimmunity; the mechanism(s) underlying this is unclear. We examined whether type 1 diabetes (T1D) polygenic risk contributes to clinical phenotype in monogenic autoimmune diabetes. Individuals with monogenic autoimmune diabetes had higher T1D genetic risk scores compared with control cohorts, driven largely by increased presence of T1D-risk DR3-DQ2 haplotype. Established T1D polygenic risk alleles, particularly class II HLA genes, contribute to clinical presentation in monogenic autoimmunity. [ABSTRACT FROM AUTHOR]

Frozen shoulder is a painful condition that often requires surgery and affects up to 5% of individuals aged 40–60 years. Little is known about the causes of the condition, but diabetes is a strong risk factor. To begin to understand the biological mechanisms involved, we aimed to identify genetic variants associated with frozen shoulder and to use Mendelian randomization to test the causal role of diabetes. We performed a genome-wide association study (GWAS) of frozen shoulder in the UK Biobank using data from 10,104 cases identified from inpatient, surgical and primary care codes. We used data from FinnGen for replication and meta-analysis. We used one-sample and two-sample Mendelian randomization approaches to test for a causal association of diabetes with frozen shoulder. We identified five genome-wide significant loci. The most significant locus (lead SNP rs28971325; OR = 1.20, [95% CI: 1.16–1.24], p = 5x10-29) contained WNT7B. This variant was also associated with Dupuytren's disease (OR = 2.31 [2.24, 2.39], p<1x10-300) as were a further two of the frozen shoulder associated variants. The Mendelian randomization results provided evidence that type 1 diabetes is a causal risk factor for frozen shoulder (OR = 1.03 [1.02–1.05], p = 3x10-6). There was no evidence that obesity was causally associated with frozen shoulder, suggesting that diabetes influences risk of the condition through glycemic rather than mechanical effects. We have identified genetic loci associated with frozen shoulder. There is a large overlap with Dupuytren's disease associated loci. Diabetes is a likely causal risk factor. Our results provide evidence of biological mechanisms involved in this common painful condition. Author summary: Frozen shoulder is a painful condition that often requires surgery and affects up to 5% of individuals aged 40–60 years. Little is known about the causes but it is known to be more common in people with diabetes. In a dataset of 500,000 people, we used a genome-wide association study to find genetic causes and a genetic technique called Mendelian randomisation to test if diabetes causes frozen shoulder. We found five new genetic variants that associate with frozen shoulder, and showed genetic overlap with Dupuytren's Disease, a similar condition that affects the fingers. We found an association with diabetes and obesity, but that the obesity association disappeared when we accounted for diabetes status, suggesting the condition is glycaemic rather than mechanical. Our Mendelian randomisation study showed evidence that type 1 diabetes has a causal effect on development of frozen shoulder, likely through a pathway involving long-term high blood glucose levels. [ABSTRACT FROM AUTHOR]