Systemic sclerosis and organic solvents: early diagnosis in industry

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.

The pathogenesis of systemic sclerosis revisited

Although infectiological stimuli, environmental factors and genotypic features are known to contribute to the initiation and perpetuation of systemic sclerosis (SSc), its etiology still remains to be enigmatic, and less elusive insights are to be achieved by ongoing and future investigations. Being characterized, however, as chronic autoimmune disease with excessive collagen accumulation in skin, synovia and visceral organs such as lung, heart, and digestive tract along with obliterating angiopathy, the pathophysiology of SSc can be summarized as being based on imbalances of the cellular and humoral immune system, vascular dysfunction and activation of resident connective tissue cells. A complex interplay between these major components manages to establish and maintain the inability of the vasculature to adequately react to the need for dilatation, constriction and growth of new vessels, to cause the increased deposition of extracellular matrix constituents as well as to facilitate immunological disarrangement. Despite parallels to the chicken and egg causality dilemma, all of these account for what later clinicians observe in patients suffering from Raynaud's phenomenon, digital ulcers, sclerodactyly, rigidity of the face, microstomia, sicca syndrome, dyspnea, dry cough, pulmonary hypertension, palpitations, syncopes, renal insufficiency, dysphagia, gastroesophageal reflux, dyspepsia, generalized arthralgias, but also dyspareunia, or erectile dysfunction.

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.

Cytochrome P2 polymorphisms and susceptibility to scleroderma following exposure to organic solvents

OBJECTIVE

To determine whether there are specific cytochrome P450 (CYP2) alleles that increase susceptibility to scleroderma in individuals who have been exposed to organic solvents.

METHODS

CYP alleles at 2 loci, 2E1 and 2C19, were compared in 7 patients who had developed scleroderma after exposure to solvents versus 71 patients with scleroderma without solvent exposure ("sporadic" disease) and 106 population controls.

RESULTS

The 2E1*3 allele was found in 2 of the 7 patients who had been exposed to organic solvents, with a greater frequency than occurred in either the disease controls or the population controls (odds ratio [95% confidence interval] 9.1 [1.5-59.1] and 10.2 [1.8-62.2], respectively). All 7 patients with solvent exposure carried the 2C19EM genotype, compared with 89% of patients with sporadic scleroderma.

CONCLUSION

Our results suggest that alleles at CYP loci may be involved in increasing susceptibility to scleroderma among subjects who have been exposed to organic solvents.

Increased numbers of microchimeric cells of fetal origin are associated with dermal fibrosis in mice following injection of vinyl chloride

OBJECTIVE

To develop a murine model for use in examining the role of microchimeric cells and certain chemical exposures in the pathogenesis of systemic sclerosis (SSc).

METHODS

Female BALB/cJ retired breeder mice were bled before and after vinyl chloride injection. The DNA from their white blood cells was obtained, and the number of microchimeric cell equivalents was determined by quantitative polymerase chain reaction using DNA primers specific for the H-2Kb gene, a sequence not found in BALB/cJ mice. Skin was obtained at autopsy, embedded in paraffin, sectioned, and stained with Masson's trichrome. Hydroxyproline analyses were performed on 4-mm skin biopsy samples.

RESULTS

Microchimeric cells were identified and quantitated before and after 20 daily intraperitoneal injections of vinyl chloride. The number of microchimeric cells in the peripheral blood increased an average of 48-fold after treatment with vinyl chloride. Histologic examination of the skin of these same mice (which had an increased number of microchimeric cells) showed inflammation, with abundant fibroblasts and a heavy mononuclear infiltration in the dermis. The collagen fibers appeared densely packed and disorganized. Histologic examination of the skin of untreated retired breeder mice and treated virgin mice appeared normal. Quantitative assays to determine the collagen content of skin biopsy samples obtained from treated microchimeric mice compared with nontreated microchimeric or with treated nonmicrochimeric mice showed a 2-3-fold increase in collagen content in the treated microchimeric mice. Extraordinary splenomegaly was present in the vinyl chloride-treated microchimeric mice, accompanied by cellular infiltration and fibrosis.

CONCLUSION

The results suggest that vinyl chloride injections into BALB/cJ retired breeder mice lead to activation of microchimeric cells, which causes the cells to divide and multiply. The correlation between the 48-fold increase in microchimeric cells and the appearance of dermal inflammation and fibrosis similar to that of graft-versus-host disease suggests that activated microchimeric cells may be a necessary factor in the pathogenesis of autoimmune diseases such as SSc.

Epidemiology of organic solvents and connective tissue disease

Case reports suggest that solvents are associated with various connective tissue diseases (systemic sclerosis, scleroderma, undifferentiated connective tissue disease, systemic lupus erythematosis, and rheumatoid arthritis), particularly systemic sclerosis. A small number of epidemiological studies have shown statistically significant but weak associations between solvent exposure, systemic sclerosis, and undifferentiated connective tissue disease. However, the interpretation of these positive findings is tempered by a lack of replication, an inability to specify which solvents convey risk, and an absence of increasing risk with increasing exposure. Existing studies, on aggregate, do not show conclusively that solvents (either as a group of chemicals or individual chemicals) are causally associated with any connective tissue disease. Further investigations should be carried out to replicate the positive existing findings and to specify the solvents and circumstances of exposure that carry risk.

Occupational and environmental influences on scleroderma

This article has reviewed available data on the environmental agents, including occupational factors, that might influence susceptibility to scleroderma. None of the exposures considered could act independently in causing the disease and individually would only be responsible for a small proportion of cases. Nonetheless, they do provide useful insight into the possible mechanisms of disease causation.

Segregation of autoantibodies with disease in monozygotic twin pairs discordant for systemic sclerosis. Three further cases

OBJECTIVE

To study the serologic status of 3 previously unreported monozygotic twin pairs discordant for systemic sclerosis (SSc).

METHODS

Autoantibodies were measured by indirect immunofluorescence, immunodiffusion, and immunoprecipitation of 35S-labeled cell lines. Major histocompatibility complex (MHC) class II allele typing and DNA fingerprinting were used to confirm monozygosity.

RESULTS

Anti-PM-Scl, anti-threonyl transfer RNA synthetase, and anti-topoisomerase I antibodies, respectively, were found in each of the twins with SSc. None of the unaffected twin siblings had an identifiable autoantibody, although serum from 1 unaffected twin precipitated several unknown proteins. The MHC class II genotype in each twin was the genotype expected for the autoantibody that was present.

CONCLUSION

Autoantibodies of certain defined specificities are intimately linked with the development of SSc, because they segregate with SSc in individuals who start life with identical germline genes.

Occupational scleroderma. A 17-year follow-up study

Two patients with a scleroderma-like disorder induced by epoxy resins were reported from the Department of Dermatology, Gunma University School of Medicine, Japan in 1980. Here, we describe the clinical and laboratory characteristics of these patients after 17 years' follow-up from 1976 to 1993. Their systemic manifestations and indurated sclerotic skin changes disappeared within 5 years. No internal organ involvement has developed during the period of follow-up. On routine laboratory tests, no abnormalities have been found in the peripheral blood or in the blood chemistry or serology. Histological examination revealed atrophy of the dermis and restoration of the normal pattern of fine collagen bundles, when compared with the previous skin biopsy specimens. This scleroderma-like disorder induced by epoxy resins is considered to be different from systemic sclerosis: it has an acute onset and a fairly good prognosis, and does not show involvement of the internal organs.