Polygenic risk assessment reveals pleiotropy between sarcoidosis and inflammatory disorders in the context of genetic ancestry.

Sarcoidosis is a complex disease of unknown etiology characterized by the presence of granulomatous inflammation. Though various immune system pathways have been implicated in disease, the relationship between the genetic determinants of sarcoidosis and other inflammatory disorders has not been characterized. Herein, we examined the degree of genetic pleiotropy common to sarcoidosis and other inflammatory disorders to identify shared pathways and disease systems pertinent to sarcoidosis onset. To achieve this, we quantify the association of common variant polygenic risk scores from nine complex inflammatory disorders with sarcoidosis risk. Enrichment analyses of genes implicated in pleiotropic associations were further used to elucidate candidate pathways. In European-Americans, we identify significant pleiotropy between risk of sarcoidosis and risk of asthma (R2=2.03%; P=8.89 × 10-9), celiac disease (R2=2.03%; P=8.21 × 10-9), primary biliary cirrhosis (R2=2.43%; P=2.01 × 10-10) and rheumatoid arthritis (R2=4.32%; P=2.50 × 10-17). These associations validate in African Americans only after accounting for the proportion of genome-wide European ancestry, where we demonstrate similar effects of polygenic risk for African-Americans with the highest levels of European ancestry. Variants and genes implicated in European-American pleiotropic associations were enriched for pathways involving interleukin-12, interleukin-27 and cell adhesion molecules, corroborating the hypothesized immunopathogenesis of disease.

Sarcoidosis does not belong to or overlap with immunoglobulin G4-related diseases based on an assessment of serum immunoglobulin G4 levels in cardiac and noncardiac sarcoidosis.

Although sarcoidosis may exhibit histopathologic features similar to those of a newly emerging clinical entity, immunoglobulin G4-related sclerosing disease, sarcoidosis is currently not considered to be associated with immunoglobulin G4-related immunoinflammation. Not many studies on this association have been reported. We investigated serum immunoglobulin G4 levels among patients with sarcoidosis with or without cardiac involvement (cardiac sarcoidosis and non-cardiac sarcoidosis patients). The mean serum immunoglobulin G4 level among the 65 patients with sarcoidosis was 56.8 ± 43.0 mg/dL, which did not significantly differ between patients with cardiac sarcoidosis (54 ± 48 mg/dL, n = 12) and patients without cardiac sarcoidosis (58 ± 42 mg/dL; n = 53). Serum level of soluble interleukin 2 receptor, a potent marker that may reflect sarcoidosis activity, was elevated in cardiac sarcoidosis (910 ± 683 U/L) and noncardiac sarcoidosis (689 ± 399 U/L) but did not significantly differ between the groups. Immunohistochemistry of cardiac or lymph node specimens from patients with cardiac sarcoidosis showed only sparse or no infiltration of immunoglobulin G4-positive lymphocytes, in contrast to the moderate to severe infiltration of CD68-positive macrophages and CD45-positive lymphocytes. Although the number of study subjects was small, these findings collectively suggest that regardless of the presence or absence of cardiac involvement, sarcoidosis does not belong to or overlap with immunoglobulin G4-related sclerosing disease.

Inflammatory activity assessment by F18 FDG-PET/CT in persistent symptomatic sarcoidosis.

BACKGROUND: Establishing inflammatory activity in sarcoidosis patients with persistent disabling symptoms is important. Whole body F(18)-FDG PET/CT (PET) appeared to be a sensitive method to detect inflammatory activity in newly diagnosed symptomatic sarcoidosis. The aim was to assess the presence of inflammatory activity using PET in sarcoidosis patients with unexplained persistent disabling symptoms and the association between PET findings and serological inflammatory markers. METHODS: Sarcoidosis patients who underwent a PET between June 2005 and June 2010 (n = 89), were retrospectively included. All PET scans were examined and positive findings were classified as thoracic and/or extrathoracic. As serological markers of inflammatory activity angiotensin-converting enzyme (ACE), soluble interleukin-2 receptor (sIL-2R), and neopterin were considered. RESULTS: In 65/89 (73%) of the studied patients PET was positive, 52 of them (80%) had serological signs of inflammatory activity. In 14/15 patients with a Chest X-ray stage IV PET was positive. In 80% of the PET positive patients extrathoracic inflammatory activity was found. Sensitivity of combined serological inflammatory markers for the presence of inflammatory activity as detected by PET was 80%, specificity 100%, positive predictive value 100%, negative predictive value 65%. CONCLUSIONS: The majority of sarcoidosis patients with persistent disabling symptoms, even those with radiological stage IV, had PET positive findings with remarkably 80% extrathoracic lesions. In 20% PET was positive without signs of serological inflammatory activity. PET appeared to be of additional value to assess inflammatory activity in patients with persistent symptoms in the absence of signs of serological inflammatory activity and to detect extrathoracic lesions.

An assessment of peripheral immunity in patients with sarcoidosis using measurements of serum vitamin D3, cytokines and soluble CD23.

The aetiology of the peripheral anergy in sarcoidosis is unclear. To investigate this further we measured the serum levels of several factors important in different aspects of immune regulation to obtain a profile of those factors which promote and inhibit immune activation in sarcoidosis. Thirty-seven patients with sarcoidosis and 20 healthy controls of similar sex and age comprised the study group. Serum IL-10, interferon-gamma (IFN-gamma), soluble CD23 (sCD23), IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-1beta and tumour necrosis factor-alpha (TNF-alpha) were measured using in-house ELISAs. Vitamin D3 was measured using a radioreceptor assay. Serum levels of sCD23 and IL-10 were significantly elevated in patients with sarcoidosis relative to controls (median 13.9 versus 9.5 arbitrary units/ml, P<0.01 for sCD23, and 9.6 versus 5.0 pg/ml, P<0.04 for IL-10). Regardless of steroid therapy or disease activity, serum levels of IFN-gamma, TNF-alpha, IL-1beta, GM-CSF and IL-8 were no different in patients with sarcoidosis and controls. Vitamin D3 levels were significantly higher in patients with sarcoidosis versus normal controls (medians 78.0 versus 56.0, P<0.001), active sarcoidosis (n = 20) versus inactive disease (n = 17) (medians 81.5 versus 66.0, P<0.03) and active sarcoidosis versus controls (medians 81.5 versus 56.0, P<0.0002). The levels were no different between patients with inactive sarcoidosis and controls. We suggest that IL-10 and vitamin D3 may contribute to the peripheral anergy in sarcoidosis. The elevated serum sCD23 suggests an increase in peripheral humoral immunity. Consistent with a quiescent peripheral immune system, factors capable of monocyte/macrophage activation (TNF-alpha, IFN-gamma, GM-CSF and IL-8) were not elevated in the peripheral circulation.

Immunopathogenesis, immunology and assessment of activity of sarcoidosis.

To this point we have attempted to summarize what we believe to be the most exciting new findings relative to sarcoidosis, along with providing data in support of those comments. We wish to conclude this brief review by sharing some anecdotal thoughts (no benefit of controlled clinical trials) concerning how the individual practitioner may apply this "research" information in caring for patients. In newly diagnosed patients with sarcoidosis, especially with widespread use of transbronchial lung biopsy, we would recommend BAL at that time because it can provide very valuable information with minimal increased morbidity or cost. BAL, in combination with SACE and possibly gallium scan (not required in all), along with the usual measures such as pulmonary function studies, chest roentgenograms (all of which are already commonly done) permit the clinician to make an accurate conclusion about disease activity in the lungs. Because there are no published therapeutic trials of corticosteroids in which the ultimate prognosis of pulmonary sarcoidosis has been improved, the decision to initiate therapy in these patients remains a clinical one and is commonly based upon practitioner experience rather than a particular laboratory test per se. Once that decision has been made, a decision to repeat any "research" studies would have to be individualized. Clearly serial SACE measures are relatively inexpensive and without morbidity. Moreover, despite their lack of "diagnostic value" serial measurements in known sarcoidosis have been shown to be very valuable in assessing disease activity and may therefore provide the clinician with a valuable aid to monitoring steroid treatment. A less common and much more perplexing circumstance occurs when evaluating patients with sarcoidosis established for several years present with evidence of progressive or chronic pulmonary involvement and dyspnea. In such individuals a measure of activity would be very helpful because the clinician would like to avoid steroids in persons with end stage and irreversible fibrosis and consider their use in those individuals in whom there is evidence of continued disease activity. In this instance, gallium scan, SACE and even BAL may all prove valuable. When we have found SACE elevated and gallium scan positive, we have assumed the disease to be active (even if the chest X-rays show stability).(ABSTRACT TRUNCATED AT 400 WORDS)