Systemic sclerosis associated with cutaneous exposure to solvent: case report and review of the literature

Risk factors for the development of systemic sclerosis: a systematic review of the literature

OBJECTIVES

Although numerous studies have investigated the roles of various genetic, epigenetic and environmental factors that may impact its aetiology, SSc is still regarded as an idiopathic disease. Given that there is significant heterogeneity in what has been proposed to influence the development of SSc, this systematic review was conducted to assess the impacts of different factors on the aetiology of scleroderma.

METHODS

The search was performed in the PubMed, CINAHL and SCOPUS databases on 17 May 2017. Any study that made explicit reference to scleroderma or SSc that had information about the risk factors or epidemiology of the disease was included. The extracted outcome variables were prevalence, gender preponderance, geographical distribution, family history and various proposed environmental risk factors.

RESULTS

One thousand five hundred and seventy-four articles were screened for eligibility. Thirty-four articles were eligible for the systematic literature review.

CONCLUSION

Age between 45 and 64 years, female sex, positive family history and exposure to silica were found to be risk factors. There were conflicting findings regarding the impact of exposure to organic solvents and microchimerism. No relationship between infectious agents, alcohol consumption or cigarette smoking and the development of SSc was identified.

Organic solvents as risk factor for autoimmune diseases: a systematic review and meta-analysis

BACKGROUND

Genetic and epigenetic factors interacting with the environment over time are the main causes of complex diseases such as autoimmune diseases (ADs). Among the environmental factors are organic solvents (OSs), which are chemical compounds used routinely in commercial industries. Since controversy exists over whether ADs are caused by OSs, a systematic review and meta-analysis were performed to assess the association between OSs and ADs.

METHODS AND FINDINGS

The systematic search was done in the PubMed, SCOPUS, SciELO and LILACS databases up to February 2012. Any type of study that used accepted classification criteria for ADs and had information about exposure to OSs was selected. Out of a total of 103 articles retrieved, 33 were finally included in the meta-analysis. The final odds ratios (ORs) and 95% confidence intervals (CIs) were obtained by the random effect model. A sensitivity analysis confirmed results were not sensitive to restrictions on the data included. Publication bias was trivial. Exposure to OSs was associated to systemic sclerosis, primary systemic vasculitis and multiple sclerosis individually and also to all the ADs evaluated and taken together as a single trait (OR: 1.54; 95% CI: 1.25-1.92; p-value<0.001).

CONCLUSION

Exposure to OSs is a risk factor for developing ADs. As a corollary, individuals with non-modifiable risk factors (i.e., familial autoimmunity or carrying genetic factors) should avoid any exposure to OSs in order to avoid increasing their risk of ADs.

Gender differences in autoimmunity associated with exposure to environmental factors

Autoimmunity is thought to result from a combination of genetics, environmental triggers, and stochastic events. Gender is also a significant risk factor with many diseases exhibiting a female bias. Although the role of environmental triggers, especially medications, in eliciting autoimmunity is well established less is known about the interplay between gender, the environment and autoimmunity. This review examines the contribution of gender in autoimmunity induced by selected chemical, physical and biological agents in humans and animal models. Epidemiological studies reveal that environmental factors can be associated with a gender bias in human autoimmunity. However many studies show that the increased risk of autoimmunity is often influenced by occupational exposure or other gender biased activities. Animal studies, although often prejudiced by the exclusive use of female animals, reveal that gender bias can be strain specific suggesting an interaction between sex chromosome complement and background genes. This observation has important implications because it argues that within a gender biased disease there may be individuals in which gender does not contribute to autoimmunity. Exposure to environmental factors, which encompasses everything around us, adds an additional layer of complexity. Understanding how the environment influences the relationship between sex chromosome complement and innate and adaptive immune responses will be essential in determining the role of gender in environmentally-induced autoimmunity.

Systemic sclerosis: environmental factors

Epidemiological evidence for the association between environmental and occupational risk factors and systemic sclerosis (SSc) has been extensively analyzed. Such exposures are frequently of long duration, and the inadequate classification of the type of exposure and other confounding variables may bias their estimated association with SSc. Environmental factors could be classified as occupational (silica, organic solvents), infectious (bacterial, viral), and non-occupational/non-infectious (drugs, pesticides, silicones). Understanding the link between environmental risk factors and the development of SSc is limited, due to the phenotypic and pathogenic heterogeneity of patients and disease, respectively, and also due to poor ability to assess environmental exposures quantitatively and the role of the gene-environment interactions in this disease. Global collaboration could increase the chance for a better use of the data obtained from a limited number of cases and also limited resources. Normalization and validation of biomarkers and questionnaires could also be very useful to reliably quantify environmental exposures.

Assessment of trichloroethylene (TCE) exposure in murine strains genetically-prone and non-prone to develop autoimmune disease

There is increasing laboratory and epidemiologic evidence relating exposure to trichloroethylene (TCE) with autoimmune disease including scleroderma and lupus. New Zealand Black/New Zealand White (NZBWF1) and B6C3F1 mice were exposed to TCE (0, 1, 400 or 14,000 ppb) via drinking water for 27 or 30 weeks, respectively. NZBWF1 mice spontaneously develop autoimmune disease while B6C3F1 mice, a standard strain used in immunotoxicology testing, are not genetically prone to develop autoimmune disease. During the TCE exposure period, serum levels of total IgG, and autoantibodies (anti-ssDNA, -dsDNA, and -glomerular antigen [GA]) were monitored. At the termination of the study, renal pathology, natural killer (NK) cell activity, total IgG levels, autoantibody production, T-cell activation, and lymphocytic proliferative responses were evaluated. TCE did not alter NK cell activity, or T- and B-cell proliferation in either strain. Numbers of activated T-cells (CD4+/CD44+) were increased in the B6C3F1 mice but not in the NZBWF1 mice. Renal pathology, as indicated by renal score, was significantly increased in the B6C3F1, but not in the NZBWF1 mice. Serum levels of autoantibodies to dsDNA and ssDNA were increased at more time points in B6C3F1, as compared to the NZBWF1 mice. Anti-GA autoantibodies were increased by TCE treatment in early stages of the study in NZBWF1 mice, but by 23 weeks of age, control levels were comparable to those of TCE-exposed animals. Serum levels anti-GA autoantibodies in B6C3F1 were not affected by TCE exposure. Overall, these data suggest that TCE did not contribute to the progression of autoimmune disease in autoimmune-prone mice during the period of 11-36 weeks of age, but rather lead to increased expression of markers associated with autoimmune disease in a non-genetically prone mouse strain.

Chronic exposure to trichloroethene causes early onset of SLE-like disease in female MRL +/+ mice

Trichloroethene (TCE) exacerbates the development of autoimmune responses in autoimmune-prone MRL +/+ mice. Although TCE-mediated autoimmune responses are associated with an increase in serum immunoglobulins and autoantibodies, the underlying mechanism of autoimmunity is not known. To determine the progression of TCE-mediated immunotoxicity, female MRL +/+ mice were chronically exposed to TCE through the drinking water (0.5 mg/ml of TCE) for various periods of time. Serum concentrations of antinuclear antibodies increased after 36 and 48 weeks of TCE exposure. Histopathological analyses showed lymphocyte infiltration in the livers of MRL +/+ mice exposed to TCE for 36 or 48 weeks. Lymphocyte infiltration was also apparent in the pancreas, lungs, and kidneys of mice exposed to TCE for 48 weeks. Immunoglobulin deposits in kidney glomeruli were found after 48 weeks of exposure to TCE. Our results suggest that chronic exposure to TCE promotes inflammation in the liver, pancreas, lungs, and kidneys, which may lead to SLE-like disease in MRL +/+ mice.

Differential immune responses to albumin adducts of reactive intermediates of trichloroethene in MRL+/+ mice

Trichloroethene (TCE) is an industrial degreasing solvent and widespread environmental contaminant. Exposure to TCE is associated with autoimmunity. The mode of action of TCE is via its oxidative metabolism, and most likely, immunotoxicity is mediated via haptenization of macromolecules and subsequent induction of immune responses. To better understand the role of protein haptenization through TCE metabolism, we immunized MRL+/+ mice with albumin adducts of various TCE reactive intermediates. Serum immunoglobulins and cytokine levels were measured to determine immune responses against haptenized albumin. We found antigen-specific IgG responses of the IgG subtypes IgG(1), IgG(2a), and IgG(2b), with IgG(1) predominating. Serum levels of G-CSF were increased in immunized mice, suggesting macrophage activation. Liver histology revealed lymphocyte infiltration in the lobules and the portal area following immunization with formyl-albumin. Our findings suggest that proteins haptenized by metabolites of TCE may act as neo-antigens that can induce humoral immune responses and T cell-mediated hepatitis.

Autoimmune response in MRL+/+ mice following treatment with dichloroacetyl chloride or dichloroacetic anhydride

Dichloroacetyl chloride (DCAC) is formed from trichloroethene (TCE), which is implicated in inducing/accelerating autoimmune response. Due to its potent acylating activity, DCAC may convert proteins to neo-antigens and thus could induce autoimmune responses. Dichloroacetic anhydride (DCAA), which is a similar acylating agent, might also induce autoimmune responses. To evaluate if chloroacylation plays a role in the induction of autoimmunity, we have measured the autoimmune responses following treatment with DCAC or DCAA in autoimmune-prone MRL+/+ mice. Five-week-old female mice were injected intraperitoneally (twice weekly) with 0.2 mmol/kg of DCAC or DCAA in corn oil for 6 weeks. Total serum IgG, IgG1, and IgE levels were significantly increased in DCAC-treated mice as compared to controls. These increases corresponded with increases in DCAC-specific IgG and IgG1 levels. Total serum IgM was decreased in both DCAC- and DCAA-treated mice. Antinuclear antibodies, measured as an indication of systemic autoimmune responses, were increased in both DCAC- and DCAA-treated mice. Of eight Th1/Th2 cytokines measured in the serum, only IL-5 was significantly decreased in both treatment groups. The cytokine secretion patterns of splenic lymphocytes after stimulation with antibodies against CD3 (T cell receptor-mediated signal) and CD28 (costimulatory signal) differed between treatment and control groups. Levels of IL-1, IL-3, IL-6, IFN-gamma, G-CSF, and KC were higher in cultures of stimulated splenocytes from either DCAC- or DCAA-treated mice than from controls. The level of IL-17 was only increased in cultures from DCAC-treated mice. Increased lymphocytic populations were found in the red pulp of spleens following treatment with either DCAC or DCAA. In addition, thickening of the alveolar septa in the lungs of DCAC- or DCAA-treated mice was observed. The lung histopathology in exposed mice was consistent with the symptomology observed in welders exposed to DCAC/phosgene. Thickening was more pronounced in DCAC-treated mice. Our data suggest that DCAC and DCAA elicit autoimmune responses in MRL+/+ mice that might be reflective of their chloroacylation potential in vivo.

Systemic vasculitis and prior recent exposure to organic solvents: report of two cases

The authors describe two patients with systemic vasculitis and prior occupational exposure to organic solvents. Systemic vasculitis should be considered a sentinel event for such exposures.

Systemic scleroderma: a spatiotemporal clustering

BACKGROUND AND AIMS

The aetiology of systemic scleroderma remains poorly understood. Twin studies suggest a low genetic input. Of the incriminated environmental agents, silica and vinyl chloride monomer exposure appear the most convincing. Spatiotemporal clustering has been demonstrated only three times previously. We now report a fourth cluster around Edenhope, western Victoria in terms of numerator and denominator estimates, cumulative incidence, distribution in time and space, and possible aetiological factors.

METHODS

Prevalence/cumulative incidence numerator and denominator values were obtained and validated. Each case was age-and gender-matched with two controls. A standardized postal questionnaire was used to obtain data on current, past history, family history, and occupational and non-occupational environmental exposure.

RESULTS

Six systemic scleroderma cases and one mixed connective tissue disease patient with a predominance of scleroderma features were identified. The 5-year cumulative incidence was 6.1/10,000, tenfold higher than the Sydney estimates for a similar, though non-identical time period. The gender ratio was 1:1. No cases were genetically related. A family history of scleroderma was validated in one instance and a family history of Raynaud's was noted in first degree relatives of two cases and one control. In all instances, Edenhope residence preceded disease onset. No one environmental agent was implicated in all cases.

CONCLUSION

A spatiotemporal cluster of systemic scleroderma was confirmed and validated. It occurred with a tenfold increased cumulative incidence to that expected and also extended beyond the initially defined 50 km radius of Edenhope. The cases identified were not related. Although no one specific environmental agent was identified, the spatiotemporal clustering would be compatible with an agent occurring at relatively high frequency, but with low disease conversion rates, such as silica inhalation (assuming sufficiently small particle size) or reaction to an infective agent.

A case-control study of occupational exposures and systemic sclerosis

OBJECTIVES

A case-control study was conducted in Verona, Italy, to assess the relationship between occupation, occupational exposures and systemic sclerosis (SSc).

METHODS

Fifty-five cases (46 female and nine male) and 171 controls were recruited. Interviews provided work histories, including job titles, industry and likelihood of occupational exposure to silica, hand-arm vibration, organic solvents, and other chemicals. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated.

RESULTS

Female teachers (OR 3.4, 95% CI 1.2-10.1) and textile workers (OR 2.1, 95% CI 1.0-4.6) were at an increased risk of SSc. Compared with those never exposed, age-adjusted and gender-adjusted ORs were 2.3 (95% CI 1.0-5.4) among subjects exposed to organic solvents, 2.5 (95% CI 0.8-8.0) for exposure to selected chemicals, 1.7 (95% CI 0.4-7.6) for exposure to silica, and 1.5 (95% CI 0.5-4.8) for usage of vibrating tools. When data analysis was stratified according to gender, only men showed a significant increase in risk for exposure to solvents and selected chemicals.

CONCLUSIONS

The findings of this study tend to support the role of organic solvents and certain chemicals in SSc causation. The association with teaching and working in the textile industry suggests that other exposures are involved in the aetiology of SSc among women. However, because of the small number of subjects, particularly in stratified analyses, chance cannot be ruled out as an explanation of some findings of this study.

Meta-analysis of systemic sclerosis and exposure to solvents

BACKGROUND

Although systemic sclerosis is a rare disease, incidence rates have increased recently in the United States. This study investigated the association between systemic sclerosis and exposure to solvents.

METHODS

A Medline search of articles published between 1966 and 2000 dealing with solvent exposure and systemic sclerosis identified eight studies that met inclusion criteria of the meta-analysis. The studies included seven case-control studies and one cohort study published between 1989 and 1998. A series of meta-analyses of studies on systemic sclerosis and solvent exposure were performed for all studies and for case-control studies. A random effect model was used to calculate a combined estimator of relative risk.

RESULTS

The combined estimator of relative risk for all studies was 2.91, with a 95% confidence interval (CI) of 1.60 to 5.30. The combined estimator of relative risk for the seven case-control studies was 3.14 (95% CI, 1.56-6.33).

CONCLUSIONS

A statistically significant increased relative risk for all studies and for case-control studies suggests that exposure to organic solvent may be a risk factor for developing systemic sclerosis. Further studies using other study designs and better control of confounders are needed.

ATSDR evaluation of health effects of chemicals. V. Xylenes: health effects, toxicokinetics, human exposure, and environmental fate

Xylenes, or dimethylbenzenes, are among the highest-volume chemicals in production. Common uses are for gasoline blending, as a solvent or component in a wide variety of products from paints to printing ink, and in the production of phthalates and polyester. They are often encountered as a mixture of the three dimethyl isomers, together with ethylbenzene. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites that are of greatest concern for public health purposes. These profiles comprehensively summarize toxicological and environmental information. This article constitutes the release of the bulk of this profile (ATSDR, 1995) into the mainstream scientific literature. An extensive listing of known human and animal health effects, organized by route, duration, and end point, is presented. Toxicological information on toxicokinetics, biomarkers, interactions, sensitive subpopulations, reducing toxicity after exposure, and relevance to public health is also included. Environmental information encompasses physical properties, production and use, environmental fate, levels seen in the environment, analytical methods, and a listing of regulations. ATSDR, as mandated by CERCLA (or Superfund), prepares these profiles to inform and assist the public.

Is occupational organic solvent exposure a risk factor for scleroderma?

OBJECTIVE

The primary objective was to determine whether occupational exposure to organic solvents is related to an increased risk of systemic sclerosis (SSc; scleroderma).

METHODS

Occupational histories were obtained from 178 SSc patients and 200 controls. Exposure scores were computed for each individual using job exposure matrices, which were validated by an industrial expert.

RESULTS

Among men, those with SSc were more likely than controls to have a high cumulative intensity score (odds ratio [OR] 2.9, 95% confidence interval [95% CI] 1.1-7.6) and a high maximum intensity score (OR 2.9, 95% CI 1.2-7.1) for any solvent exposure. They were also more likely than controls to have a high maximum intensity score for trichloroethylene exposure (OR 3.3, 95% CI 1.0-10.3). Among men and women, significant solvent-disease associations were observed among SSc patients who tested positive for the anti-Scl-70 autoantibody; these trends were not observed among the men and women who tested negative for anti-Scl-70.

CONCLUSION

These results provide evidence that occupational solvent exposure may be associated with an increased risk of SSc.

Biological monitoring of experimental human exposure to trimethylbenzene

Trimethylbenzene (TMB) is a component of numerous commercial preparations of organic solvents (Farbasol, Solvesso, Shellsol) used in the chemical, plastics, printing and other industries. TMB is a mixture of three isomers (pseudocumene-1,2,4-TMB; mesitylene-1,3,5-TMB; hemimellitene-1,2,3-TMB). The proportion of individual isomers in the mixture differs. The aim of this study was to obtain toxicokinetic data on the absorption and elimination of trimethylbenzene and its metabolites in biological fluids and to investigate the relationship between the biological indices of exposure and the absorbed dose. Eight-hour inhalation tests were performed in a toxicological chamber, The subjects were eight volunteers aged 20-39 with no history of exposure to TMB. They were exposed to pseudocumene, mesitylene or hemimellitene at concentrations ranging from 5 to 150 mg/m3 air. Exhaled air, capillary blood and urine samples were collected before, during and after the exposure. The determinations of TMB or its metabolites were performed using gas chromatography (HP 5890 II Plus, MSD, FID). Pulmonary ventilation in the volunteers ranged from 0.56 to 1.0 m3/h. The retention of 1,2,4-TMB; 1,3,5-TMB; 1,2,3-TMB in the lungs was 68%, 67% and 71%, respectively. The elimination of TMB from capillary blood occurred in accordance with the open three-compartment model. Urinary excretion of dimethylbenzoic acids (DMBA) proceeded according to the open two-compartment model. Based on the toxicokinetic data, a simulation model of accretion and excretion of DMBA in urine during a 14-day period was developed. The highest rates of metabolite excretion and the highest quantities of DMBA in urine during 24-h intervals were observed on day 5 of exposure. The relationship between the levels of TMB or DMBA in biological material and TMB air concentration or absorbed dose were determined. To select the urine fraction suitable for determining occupational TMB exposure, linear regression analysis was performed. The biological exposure limit (BEL) for TMB has been proposed, with the current maximum allowable concentration (MAC) value of 100 mg/m3 (Polish standard) baseline value.

[Environmental factors and iatrogenic elements in systemic scleroderma and related syndromes. Review of the literature]

The etiology of scleroderma remains unknown. Although a genetic susceptibility seems to play a role, some environmental and iatrogenic factors have been suggested to trigger the disease. Contact for many months or years with natural or synthetic "toxic" products (by inhalation, cutaneous contact, injection, swallowing or surgical implant) could be implicated in the development of typical scleroderma or pseudo-scleroderma. These products are either occupational or non occupational like those used at home in daily life. We will sum up the knowledges about this subject.

Kinetics of elimination of mesitylene and 3,5-dimethylbenzoic acid after experimental human exposure

The possibility of evaluating occupational exposure to mesitylene based on the determination of unchanged solvent in capillary blood or 3,5-dimethylbenzoic acid in urine was investigated. The volunteers were exposed to mesitylene in a toxicological chamber (range 10-150 mg/m3). Concentrations of solvent or its metabolite in biological material were determined by gas chromatography. The toxicokinetic data concerning retention in the lung, absorption and elimination of mesitylene and its metabolite in biological fluids were obtained. The highest correlation coefficient value was obtained for the relationship between the absorbed dose of mesitylene and the excretion rate of 3,5-dimethylbenzoic acid in urine (r = 0.95). The biological indices of exposure for mesitylene have been proposed, taking the maximum allowable concentration (MAC) value in Poland (100 mg/m3) as the basis.

Antinuclear antibodies in patients with scleroderma (systemic sclerosis) and in their blood relatives and spouses

OBJECTIVE

To test the postulate that there is a higher prevalence of antinuclear antibodies (ANAs) in serum samples from blood relatives and from spouses of patients with scleroderma than in control samples, and that this provides evidence for both genetic and environmental factors influencing autoimmunity in scleroderma.

METHOD

Testing for ANAs was performed on 58 patients with scleroderma, 30 of their spouses, 74 first degree relatives, and 66 control subjects broadly age matched to the patients, their spouses, and about half of the relatives (siblings and parents).

RESULTS

On the basis of an ANA titre of > 40 as positive, 12 (18%) of the controls, 55 (95%) of the patients, one (3%) of the spouses and five (7%) of the relatives would be classified as positive. Thirty seven (64%) of the patients had defined specificities (ACA, Scl 70, U1 (RNP)) but none of the controls, spouses, or relatives had antibodies of these specificities.

CONCLUSION

These findings give no support to the postulate that environmental or genetic factors contribute to the ANAs in scleroderma.

Systemic sclerosis

Systemic sclerosis affects the connective tissue of various organs. It is characterized by alteration of the microvasculature with a dense inflammatory cellular infiltrate, followed by massive deposition of collagen. This review discusses diagnostic criteria, clinical subsets, survival data, clinical evaluation, epidemiology, pathogenesis, immunobiology, genetics, and therapy for systemic sclerosis in adults. Because the diagnosis of systemic sclerosis is most dependent on its cutaneous involvement, knowledge of this is essential in the evaluation and management of patients with this disorder.