Genetic polymorphism in intron 6 of the LMP7 gene in Japanese and its association with sarcoidosis

Propionibacterium acnes-associated sarcoidosis complicated by acute bird-related hypersensitivity pneumonitis

Background

The number of reports on sarcoidosis complicated by hypersensitivity pneumonitis (HP) is limited, and most describe cases complicated by chronic bird-related HP. Here, we present for the first time a case with Propionibacterium acnes-associated sarcoidosis complicated by acute bird-related HP.

Case presentation

A 62-year-old man with a past medical history of sarcoidosis was admitted to our department, and chest computed tomography showed diffuse ground-glass opacities, which appeared as he rapidly increased the number of pigeons he kept for a competition. Random transbronchial lung biopsy revealed well-formed non-caseating epithelioid granulomas, which contained positively stained substances on immunohistochemistry using the PAB antibody, a specific monoclonal antibody against P. acnes lipoteichoic acid. Poorly formed non-caseating granulomas without positively stained substances were also detected.

Conclusion

We describe the successful identification of this exceptionally rare case of sarcoidosis complicated by acute bird-related HP in which two morphologically and immunohistologically different types of granulomas were present in the same lung.

The major histocompatibility complex gene region and sarcoidosis susceptibility in African Americans

Investigators have intensively evaluated the major histocompatibility (MHC) complex for sarcoidosis susceptibility genes with the majority of reports implicating the human leukocyte antigen (HLA)-DRB1 gene. Because most studies have been performed in white and Asian populations, we sought to determine which MHC genes might be risk factors for sarcoidosis in African Americans. We genotyped six microsatellite markers spanning 11.6 megabases that overlapped the MHC region on chromosome 6p21-22 in 225 nuclear families ascertained by African American probands with a history of sarcoidosis. Using a family-based association methods approach, we performed multiallelic tests of association between each marker and sarcoidosis. A statistically significant association was detected between sarcoidosis and the DQCAR marker (p = 0.002) less than two kilobases telomeric from the HLA-DQB1 gene. Typing two additional markers in this region revealed that DQCAR-G51152 haplotypes, spanning a 38-kilobase region across the HLA-DQB1 gene, were associated with sarcoidosis on a global level (p = 0.022). Analysis of individual DQCAR and G51152 alleles showed that the DQCAR 178 (expected = 21.0; observed = 10; p = 0.0005) and G51152 217 (expected = 25.6; observed = 14; p = 0.0009) alleles were transmitted to affected offspring less often than expected; whereas the DQCAR 182 allele was transmitted more often than expected (expected = 52.6; observed = 66; p = 0.002). Our results indicate that HLA-DQB1 and not HLA-DRB1 plays an important role in sarcoidosis susceptibility in African Americans. Identification of the specific HLA-DQB1 alleles that influence sarcoidosis susceptibility in African Americans and the study of their antigenic-binding properties may reveal why African Americans suffer disproportionately from this disease.

Is there a role for microorganisms in the pathogenesis of sarcoidosis?

Sarcoidosis is a granulomatous disease that has the immunopathological features of being antigen-driven. It is a complex disease that appears to arise from the interaction of one or more triggers with an immunologically predisposed host. Previous reports of familial clustering and varying prevalence of sarcoidosis in different populations could reflect differences in ethnic predisposition or differences in local environmental exposures. This review focuses specifically on these areas that have been the subjects of intensive investigation recently. Specific focus is provided on the issue of an infective trigger and highlights popular candidates. It is concluded that microbes are a likely trigger (but not as an infection) in a genetically predisposed individual and that this initial event culminates in the sarcoidosis granulomatous response.

Surfactant gene polymorphisms and interstitial lung diseases

Pulmonary surfactant is a complex mixture of phospholipids and proteins, which is present in the alveolar lining fluid and is essential for normal lung function. Alterations in surfactant composition have been reported in several interstitial lung diseases (ILDs). Furthermore, a mutation in the surfactant protein C gene that results in complete absence of the protein has been shown to be associated with familial ILD. The role of surfactant in lung disease is therefore drawing increasing attention following the elucidation of the genetic basis underlying its surface expression and the proof of surfactant abnormalities in ILD.

Human leukocyte antigen genes may outweigh racial background when generating a specific immune response in sarcoidosis

Presented is a sarcoidosis patient of African origin, who was adopted at an early age and grew up in Sweden. This patient displayed an immune response identical to that previously reported in human leukocyte antigen (HLA)-DR17 positive Caucasian sarcoidosis patients in Scandinavia, with T-cell receptor AV2S3+ T-cells accumulating in the lungs. HLA typing also established that she was DR17 positive, which is a rare HLA type for individuals of African origin. To the authors' knowledge, this specific immune response has not previously been reported in patients of African origin. Moreover, the clinical manifestations of sarcoidosis were similar to those known to be strongly linked to HLA-DR17 in Scandinavians, i.e. with Löfgren's syndrome. The case presented here suggests certain human leukocyte antigen genes to be strongly linked to specific immune responses that are identical irrespective of the racial background. If such an immune response were important for the subsequent clinical manifestations, this case would argue for the importance of human leukocyte antigen genes in the genetic predisposition to sarcoidosis.

The influence of T cell receptor and cytokine genes on sarcoidosis susceptibility in African Americans

The pathogenesis of sarcoidosis, a multisystem granulomatous disorder, is mediated through immunoregulatory pathways. While sarcoidosis clusters in families, inherited risk factors remain undefined. In search of possible sarcoidosis susceptibility genes, we examined anonymous polymorphic genetic markers tightly linked to six different candidate gene regions on chromosomes 2q13, 5q31, 6p23-25, 7p14-15, 14q11 and 22q11. These candidate regions contain T cell receptor, interleukin (IL) and interferon regulatory factor (IRF) genes. Our study population consisted of 105 African-American sarcoidosis cases and 95 unrelated healthy controls. The allelic frequency distribution of two out of the six markers, IL-1 alpha marker (p = 0.010) on 2q13 and the F13A marker (p = 0.0006) on 6p23-25, was statistically significantly different in cases compared with controls. The two alleles most strongly associated with sarcoidosis were IL-1 alpha*137 (Odds Ratio (OR) = 2.60; 95% confidence interval (CI) = 1.36-4.98) and F13A*188 (OR = 2.42; 95% CI = 1.37-4.30). Individuals that had both of these alleles were at a six-fold increased risk for sarcoidosis (OR = 6.19; 95% CI = 2.54-15.10). Restricting the analysis to cases with at least one first or second-degree relative affected with sarcoidosis increased the OR to 15.38. IL-1 levels are elevated in sarcoidosis and the F13A marker is tightly linked to a gene that codes for a newly identified interferon regulatory factor protein (IRF-4), which is thought to play a role in T cell effector functions. Our results suggest genetic susceptibility to sarcoidosis may be conferred by more than one immune-related gene that act synergistically on disease risk.