No abstract

Objective. We have previously identified a singlenucleotide polymorphism (SNP) haplotype involving the lymphotoxin ␣ (LTA) and tumor necrosis factor (TNF) loci (termed haplotype LTA-TNF2) on chromosome 6 that shows differential association with rheumatoid arthritis (RA) on HLA-DRB1*0404 and *0401 haplotypes, suggesting the presence of additional non-HLA-DRB1 RA susceptibility genes on these haplotypes. To refine this association, we performed a case-control association study using both SNPs and microsatellite markers in haplotypes matched either for HLA-DRB1*0404 or for HLA-DRB1*0401.Methods. Fourteen SNPs lying between HLA-DRB1 and LTA were genotyped in 87 DRB1*04-positive families. High-density microsatellite typing was performed using 24 markers spanning 2,500 kb centered around the TNF gene in 305 DRB1*0401 or *0404 cases and 400 DRB1*0401 or *0404 controls. Single-marker, 2-marker, and 3-marker minihaplotypes were constructed and their frequencies compared between the DRB1*0401 and DRB1*0404 matched case and control haplotypes.Results. Marked preservation of major histocompatibility complex haplotypes was seen, with chromosomes carrying LTA-TNF2 and either DRB1*0401 or DRB1*0404 both carrying an identical SNP haplotype across the 1-Mb region between TNF and HLA-DRB1. Using microsatellite markers, we observed two 3-marker minihaplotypes that were significantly overrepresented in the DRB1*0404 case haplotypes (P ‫؍‬ 0.00024 and P ‫؍‬ 0.00097).Conclusion. The presence of a single extended SNP haplotype between LTA-TNF2 and both DRB1*0401 and DRB1*0404 is evidence against this region harboring the genetic effects in linkage disequilibrium with LTA-TNF2. Two RA-associated haplotypes on the background of DRB1*0404 were identified in a 126-kb region surrounding and centromeric to the TNF locus.

Cogan's syndrome, typified by the combination of interstitial keratitis and immune-mediated sensorineural hearing loss, is a rare condition, and commonly associated with a diagnostic delay. Using a standard search protocol, we review the literature to date, focusing on a number of key areas pertaining to diagnosis, presentation and treatment. Using a case illustration of atypical disease which led to fulminant aortic regurgitation, we highlight the need for continued and collaborative research in order to identify negative prognostic factors and thus tailor therapeutic regimens. Atypical Cogan's syndrome is more commonly associated with systemic manifestations than typical disease, and may be refractory to immunosuppressive treatment. We discuss the application of laboratory (e.g antibodies targeting inner ear antigens) and radiological (PET-CT) aids to disease confirmation and detection of sub-clinical vascular inflammation. As illustrated by the included case description, some patients remain refractory to intense immunosuppression and delineation of adverse prognostic factors which may direct treatment, perhaps including the use of PET-CT, will contribute in the future to improving patient outcomes.

The MFG test is a family-based association test that detects genetic effects contributing to disease in offspring, including offspring allelic effects, maternal allelic effects and MFG incompatibility effects. Like many other family-based association tests, it assumes that the offspring survival and the offspring-parent genotypes are conditionally independent provided the offspring is affected. However, when the putative disease-increasing locus can affect another competing phenotype, for example, offspring viability, the conditional independence assumption fails and these tests could lead to incorrect conclusions regarding the role of the gene in disease. We propose the v-MFG test to adjust for the genetic effects on one phenotype, e.g., viability, when testing the effects of that locus on another phenotype, e.g., disease. Using genotype data from nuclear families containing parents and at least one affected offspring, the v-MFG test models the distribution of family genotypes conditional on offspring phenotypes. It simultaneously estimates genetic effects on two phenotypes, viability and disease. Simulations show that the v-MFG test produces accurate genetic effect estimates on disease as well as on viability under several different scenarios. It generates accurate type-I error rates and provides adequate power with moderate sample sizes to detect genetic effects on disease risk when viability is reduced. We demonstrate the v-MFG test with HLA-DRB1 data from study participants with rheumatoid arthritis (RA) and their parents, we show that the v-MFG test successfully detects an MFG incompatibility effect on RA while simultaneously adjusting for a possible viability loss.

BackgroundClinically hypomyopathic dermatomyositis is a rare disease that is important to recognize, investigate and treat early as it is associated with poor prognosis. In a proportion of patients, myositis specific antibodies could be negative, but with high clinical suspicion, myositis associated antibodies should be ordered. Anti-MDA-5 antibodies was reported in literature to be associated with severe and rapidly progressive interstitial lung disease, with few case reports of pneumothorax and/or pneumomediastinum.Case presentationA 49-year-old previously healthy lady, presented with a 6 week history of skin rash, photosensitivity, mouth ulcers, fatiguability, arthralgia and myalgia. She denied subjective weakness, respiratory symptoms or dysphagia. She had Raynaud’s phenomenon affecting her fingers only. Initial examination showed synovitis in her hands with skin rash. Autoimmune screen was negative. She was started on hydroxychloroquine. 4 weeks later on follow-up, she developed proximal muscle pain, dysphagia, dyspnea and dry cough. Examination showed mild proximal muscle weakness and bi-basal crackles. She was admitted and extended myositis screen was sent. She had mild anemia, lymphopenia and neutropenia, normal inflammatory markers, liver and renal panels. Capillaroscopy showed pattern of systemic sclerosis. CT chest showed early ILD. Electromyography and MRI showed features of mild myositis. PFT showed muscle weakness with low DLCO. She was given intravenous steroid and Rituximab. As she continued to deteriorate, intravenous immunoglobulins and cyclophosphamide were given. There was a brief clinical response that was short-lived with increasing oxygen dependency necessitating transfer to the ICU. At this point, the extended myositis screen confirmed the presence of anti-MDA-5 antibodies. She commenced plasmapharesis and required intubation. Unfortunately, she developed multiple pneumothoraces, and was transferred urgently for ECMO. Subsequent immunosuppression included rituximab and tacrolimus. There was progression of her ILD and recurrent pneumothoraces and pneumomediastinum. Unfortunately, she passed away as a consequence of her disease.ConclusionThis case highlights a number of considerations in approaching patients with inflammatory myositis, particularly to pulmonary involvement. It is important to highlight the utility of extended myositis antibody testing in predicting disease phenotypes and its impact on therapeutic decisions. From a management perspective, aggressive immunosuppression should be considered with potential need of earlier utilization of ECMO.