A case of IgG4oligoarthritis mimicking psoriatic arthritis.

IgG4-related disease (IgG4-RD) is a rare but rapidly emerging immune-mediated fibroinflammatory condition that can affect almost any organ. It is typically associated with involvement of organs such as lymph nodes, submandibular glands, orbits, periaortic region and pancreas. However, IgG4-RD presenting primarily as an inflammatory arthritis is much less recognised. We present a rare case of IgG4-RD mimicking psoriatic arthritis. In spite of normal circulating IgG4 plasma levels, a clinical index of suspicion was required to obtain a histopathological diagnosis. The patient's aggressive arthritis disease did not initially respond to typical disease- modifying agents such as methotrexate. Instead, we report a dramatic response to B cell depletion with rituximab. It is important to emphasise this case as a rare presentation of a rare disease. IgG4-RD is a rapidly emerging condition and the diagnosis should be considered when the alternatives do not seem to fit.

Human growth hormone 1 (GH1) gene expression: complex haplotype-dependent influence of polymorphic variation in the proximal promoter and locus control region.

The proximal promoter region of the human pituitary expressed growth hormone (GH1) gene is highly polymorphic, containing at least 15 single nucleotide polymorphisms (SNPs). This variation is manifest in 40 different haplotypes, the high diversity being explicable in terms of gene conversion, recurrent mutation, and selection. Functional analysis showed that 12 haplotypes were associated with a significantly reduced level of reporter gene expression whereas 10 haplotypes were associated with a significantly increased level. The former tend to be more prevalent in the general population than the latter (p<0.01), possibly as a consequence of selection. Although individual SNPs contributed to promoter strength in a highly interactive and non-additive fashion, haplotype partitioning was successful in identifying six SNPs as major determinants of GH1 gene expression. The prediction and functional testing of hitherto unobserved super-maximal and sub-minimal promoter haplotypes was then used to test the efficacy of the haplotype partitioning approach. Electrophoretic mobility shift assays demonstrated that five SNP sites exhibit allele-specific protein binding. An association was noted between adult height and the mean in vitro expression value corresponding to an individual's GH1 promoter haplotype combination (p=0.028) although only 3.3% of the variance of adult height was found to be explicable by reference to this parameter. Three additional SNPs, identified within sites I and II of the upstream locus control region (LCR), were ascribed to three distinct LCR haplotypes. A series of LCR-GH1 proximal promoter constructs were used to demonstrate that 1) the LCR enhanced proximal promoter activity by up to 2.8-fold depending upon proximal promoter haplotype, and that 2) the activity of a given proximal promoter haplotype was also differentially enhanced by different LCR haplotypes. The genetic basis of inter-individual differences in GH1 gene expression thus appears to be extremely complex.