Silicon nephropathy and myeloperoxidase antibodies

Antineutrophil cytoplasmic autoantibodies: how should the biologist manage them?

Antineutrophil cytoplasmic antibodies (ANCA) are directed against enzymes found in the granules of the polymorphonuclear (PMN) leukocytes. They are detected by indirect immunofluorescence microscopy assays on human ethanol fixed neutrophils. Three different fluorescence patterns can be distinguished: a cytoplasmic pattern (cANCA), a perinuclear pattern (pANCA), and an atypical pattern (aANCA). The use of other fixatives, e.g., formalin and methanol, allows differentiation between the pANCA and the antinuclear antibodies. ANCA specificity is determined by solid phase assays (ELISA, immunodot, and multiplex assay). ANCA with high titres and defined specificities (antiproteinase 3 [PR 3] or antimyeloperoxidase [MPO]) are proven to be good serological markers of active primary systemic vasculitis: c/PR 3-ANCA for Wegener's granulomatosis and p/MPO-ANCA for microscopic polyangiitis. The former have higher sensitivity and specificity for Wegener's granulomatosis than the latter for microscopic polyangiitis. ANCA with low titres and unknown specificity have been detected in a wide range of inflammatory and infectious diseases leading to a critical reappraisal of the diagnostic significance of ANCA testing. Physicians must keep in mind the possible occurrence of infectious diseases like subacute endocarditis that could be dramatically worsened by irrelevant immunosuppressive therapy. ANCA findings in certain manifestations, such as the pulmonary-renal syndrome in which massive pulmonary hemorrhage can quickly be life-threatening, warrant ANCA testing as an emergency test for patient care.

Microscopic polyangiitis after silicone breast implantation

We describe the case of a patient who developed microscopic polyangiitis (MPA) after silicone breast implantation. A 60-year-old woman who had undergone silicone breast implantation was admitted to our hospital with complaints of general malaise and hematoproteinuria. She was diagnosed as having MPA with evidence of acute progressive renal failure, pulmonary hemorrhage, and positivity for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA). A renal biopsy showed severe necrotizing and crescentic glomerulonephritis with arteriolitis. The patient received high-dose steroids and plasma exchange treatment, but died of progressive pulmonary hemorrhage and multiple cerebral hemorrhage. Silicone implantation is associated with scleroderma, systemic lupus erythematosus, and rheumatoid arthritis. This case report indicates the possibility of the development of MPA after silicone breast implantation.

Are environmental factors important in primary systemic vasculitis? A case-control study

OBJECTIVE

To investigate the association between primary systemic vasculitis (PSV) and environmental risk factors.

METHODS

Seventy-five PSV cases and 273 controls (220 nonvasculitis, 19 secondary vasculitis, and 34 asthma controls) were interviewed using a structured questionnaire. Factors investigated were social class, occupational and residential history, smoking, pets, allergies, vaccinations, medications, hepatitis, tuberculosis, and farm exposure in the year before symptom onset (index year). The Standard Occupational Classification 2000 and job-exposure matrices were used to assess occupational silica, solvent, and metal exposure. Stepwise multiple logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) adjusted for potential confounders. Total PSV, subgroups (47 Wegener's granulomatosis [WG], 12 microscopic polyangiitis, 16 Churg-Strauss syndrome [CSS]), and antineutrophil cytoplasmic antibody (ANCA)-positive cases were compared with control groups.

RESULTS

Farming in the index year was significantly associated with PSV (OR 2.3 [95% CI 1.2-4.6]), with WG (2.7 [1.2-5.8]), with MPA (6.3 [1.9-21.6]), and with perinuclear ANCA (pANCA) (4.3 [1.5-12.7]). Farming during working lifetime was associated with PSV (2.2 [1.2-3.8]) and with WG (2.7 [1.3-5.7]). Significant associations were found for high occupational silica exposure in the index year (with PSV 3.0 [1.0-8.4], with CSS 5.6 [1.3-23.5], and with ANCA 4.9 [1.3-18.6]), high occupational solvent exposure in the index year (with PSV 3.4 [0.9-12.5], with WG 4.8 [1.2-19.8], and with classic ANCA [cANCA] 3.9 [1.6-9.5]), high occupational solvent exposure during working lifetime (with PSV 2.7 [1.1-6.6], with WG 3.4 [1.3-8.9], and with cANCA 3.3 [1.0-10.8]), drug allergy (with PSV 3.6 [1.8-7.0], with WG 4.0 [1.8-8.7], and with cANCA 4.7 [1.9-11.7]), and allergy overall (with PSV 2.2 [1.2-3.9], with WG 2.7 [1.4-5.7]). No other significant associations were found.

CONCLUSION

A significant association between farming and PSV has been identified for the first time. Results also support previously reported associations with silica, solvents, and allergy.

Lymphopenia in occupational pulmonary silicosis with or without autoimmune disease

An increased prevalence of autoimmune diseases such as rheumatoid arthritis has been demonstrated in silica-exposed patients. The aim of this study was to determine the peripheral blood lymphocyte phenotype in a population of silicotic workers employed in the slate mines of the district. Silicosis was assessed in 58 patients according to the International Labor Office's criteria. Clinical and biological data including flow cytometric evaluation of the lymphocyte subsets were compared with those from 41 healthy volunteers. The silicotic patients had a higher prevalence of autoimmune diseases (6/58 versus 0/41: P < 0.05) and of elevated antinuclear antibody titres compared to the control group. A very significant decrease of total lymphocyte count (P < 0.001) involving B, T and Natural Killer cells was found in silicotic patients as compared with matched healthy volunteers. A significant increase in the percentage of activated T cells (12.3%) was observed in the silicotic group as compared to 6.5% in the control group (P = 5 x 10(-5)). Our results show that in silicotic patients, the absolute number of circulating lymphocytes is diminished with an increased proportion of activated T cells. Whether these findings could predispose to the development of autoimmune disorders is discussed.

Antimyeloperoxidase antibodies in individuals with occupational exposure to silica

OBJECTIVE

To determine the prevalence of autoantibodies to myeloperoxidase (MPO) in a series of patients exposed to silica.

METHODS

The study included 52 patients with occupational exposure to silica (mean exposure time seven years) and a control group comprising seven patients with progressive systemic sclerosis (PSS), six patients with systemic lupus erythematosus (SLE), and 15 healthy individuals. Antibodies to MPO were detected using commercial enzyme linked immunosorbent assay (ELISA) plates coated with MPO. Indirect immunoflurescence studies for antineutrophil cytoplasmic antibodies were performed using ethanol and formol fixed neutrophils. Clinical and biological data of individuals exposed to silica were recorded (published previously).

RESULTS

Antibodies to MPO were detected in 14 individuals exposed to silica (27%). There was a statistically significant difference in anti-MPO ELISA units between the healthy subjects and patients (SLE, PSS, silica exposed individuals) (p < 0.01), but no difference between the different disease groups.

CONCLUSIONS

Individuals chronically exposed to silica, whether or not they have a connective tissue disease, have levels of antibodies to MPO (as detected by ELISA) that are greater than those found in the normal population, but similar to those in patients with systemic diseases not induced by silica (SLE/PSS).