Proposed criteria for mixed-dust pneumoconiosis: Definition, descriptions, and guidelines for pathologic diagnosis and clinical correlation

doi:10.1016/j.humpath.2004.09.008

Human Pathology

Volume 35, Issue 12, December 2004, Pages 1515-1523

An outline of this consensus was presented at the 6th International Conference on Environmental & Occupational Lung Disease at Vancouver, British Columbia, Canada (February 11–14, 1999).

https://doi.org/10.1016/j.humpath.2004.09.008 Get rights and content

Abstract

We defined mixed-dust pneumoconiosis (MDP) pathologically as a pneumoconiosis showing dust macules or mixed-dust fibrotic nodules (MDF), with or without silicotic nodules (SN), in an individual with a history of exposure to mixed dust. We defined the latter arbitrarily as a mixture of crystalline silica and nonfibrous silicates. According to our definition of MDP, therefore, MDF should outnumber SN in the lung to make a pathologic diagnosis of MDP. In the absence of confirmation of exposure, mineralogic analyses can be used to support the pathologic diagnosis. The clinical diagnosis of MDP requires the exclusion of other well-defined pneumoconioses, including asbestosis, coal workers’ pneumoconiosis, silicosis, hematite miners’ pneumoconiosis, welders’ pneumoconiosis, berylliosis, hard metal disease, silicate pneumoconiosis, diatomaceous earth pneumoconiosis, carborundum pneumoconiosis, and corundum pneumoconiosis. Typical occupations associated with the diagnosis of MDP include metal miners, quarry workers, foundry workers, pottery and ceramics workers, and stonemasons. Irregular opacities are the major radiographic findings in MDP (ILO 1980), in contrast to silicosis, in which small rounded opacities predominate. Clinical symptoms of MDP are nonspecific. MDP must be distinguished from a variety of nonoccupational interstitial pulmonary disorders.

Section snippets

Historical remarks and experimental backgrounds

In 1934, Stewart and Faulds6 reported the clinicopathologic and mineralogic features of lung changes in 15 hematite miners; these features closely resemble those of mixed-dust fibrosis. Stewart and Faulds6 categorized it as “sidero-silicosis” at that time. The term mixed-dust pneumoconiosis (Mischstaubpneumokoniose) was first introduced by Uehlinger in 1946.1 According to his clinicopathologic descriptions of MDP, “mixed dust granulomas” are softer than those of the silicotic lesion, and the

Pathologic features

Three types of lesions are typically seen in individuals who are exposed to dusts containing a mixture of crystalline silica and silicates. These include macules, mixed-dust fibrotic lesions (MDF), and silicotic nodules.23 Macules are nonpalpable lesions consisting of interstitial accumulations of dust-laden macrophages. These typically show a peribronchiolar or perivascular distribution and are associated with a delicate meshwork of reticulin fibers without obvious collagenization (Fig 1).

Mineralogic analysis

Mineralogic analysis of tissue specimens may be performed in a number of different ways. One approach is the ashing of the tissue and analysis of recovered dust gravimetrically and by x-ray diffraction.25, 26 To obtain accurate identification of the mineral species, the x-ray diffraction analysis is required, employing the x-ray absorption correction.27, 28 Unfortunately, this approach requires a large sample of lung tissue. Another approach involves in situ analysis of tissue sections by

Clinical diagnosis

The diagnosis is aided by a well-documented occupational history of concomitant exposure to mixed dust as defined above. Typical occupations associated with a diagnosis of MDP include metal miners, quarry workers, foundry workers, pottery and ceramics workers, and stonemasons. Lesions found in coal workers’ pneumoconiosis and hematite miners’ pneumoconiosis are very similar to those observed in MDP.4 However, we are arbitrarily restricting the definition of MDP to exclude these and other

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Citation Excerpt :
As a result, a diagnosis of MDP was made, sparing the patient of unnecessary TB treatment. Although the prognosis of MDP is generally favourable, MDP can progress to extensive fatal fibrosis [20], and there is no specific treatment. The most important step is to remove the patient from further exposure to the causative respirable dust.
Mixed-dust pneumoconiosis (MDP) is a controversial disease with respect to diagnostic criteria. Usually, it is regarded as an occupational disease, but cases due to domestic exposure have been reported. In domestic settings, different dust sources may contribute individually or collectively to the pathogenesis.
A 56-year-old woman presented with chest nodularity on chest X-ray examination that had not resolved after 6 months of tuberculosis (TB) treatment. Her history showed significant exposure to mixed dusts caused by grinding grains with stones and the use of biomass fuel.
In residential settings, sufficient exposure to a variety of dusts, primarily silica-based dusts as well as those containing other less-fibrogenic materials, such as carbon, silicates and iron, have been shown to cause mixed-dust pneumoconiosis. In settings where the incidence of TB is very high, such as South Africa, the diagnosis of MDP might be overlooked due to the similarities of both diseases in their radiological presentations, especially when a detailed history of domestic exposure is omitted.
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A 52-year-old, nonsmoking, African-American woman with a history of obesity, hypertension, and rheumatoid arthritis was referred for workup of multiple bilateral pulmonary nodules. The pulmonary nodules were discovered incidentally while undergoing a CT scan for an abdominal mass that was radiographically diagnosed as a uterine leiomyoma. She was asymptomatic from a pulmonary standpoint without unintentional weight loss, fevers, or night sweats. Her mother and sister had a history of lung cancer. She was diagnosed with rheumatoid arthritis 5 years earlier that was controlled with adalimumab for approximately 3 years when she stopped being seen by her rheumatologist and discontinued adalimumab. During evaluation for the abdominal mass, she re-established care with a rheumatologist and was started on 40 mg prednisone daily with plans to restart adalimumab once the workup for the abdominal mass and pulmonary nodules was completed. She had undergone bariatric surgery with cholecystectomy approximately 5 years earlier, after which she experienced intentional postsurgical weight loss.
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¹: The NIKKO-Symposium on Mixed-Dust Pneumoconiosis was held October 18–19, 1997, in Nikko, Tochigi, Japan, to develop diagnostic criteria for mixed-dust pneumoconiosis under the auspices of Labour Welfare Corporation, Tokyo, Japan. The Organizing Committee included Keizo Chiyotani, Koichi Honma, Yutaka Hosoda, and Hisao Shida, and participants included Zoltán Adamis, Eduardo Algranti, Toshiharu Fuyuki, Kiyonobu Kimura, Otha Linton, Michihito Mishina, Hiroshi Morikubo, Alvaro R. Osornio-Vargas, Yoshiaki Saitoh, Yasushi Shinohara, and Hiroshi Watanabe.

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Original contributionsProposed criteria for mixed-dust pneumoconiosis: Definition, descriptions, and guidelines for pathologic diagnosis and clinical correlation1

Abstract

Section snippets

Historical remarks and experimental backgrounds

Pathologic features

Mineralogic analysis

Clinical diagnosis

Br J Tuberc Dis Chest

Dis Chest

Exp Pathol

Chest

Mayo Clin Proc

Chest

Hum Pathol

Hum Pathol

Über Mischstaubpneumokoniosen

Schweiz Z Pathol Bakt

Industrial lung diseases of iron and steel foundry workers

Pulmonary fibrosis in non-ferrous foundry workers

Br J Ind Med

Diseases due to silica

Pulmonary fibrosis in aluminum oxide workers. Investigation of nine workers, with pathologic examination and microanalysis in three of them

Am Rev Respir Dis

The pulmonary fibrosis of haematite miners

J Pathol Bacteriol

The relationship between lung dust and lung pathology in pneumoconiosis

Br J Ind Med

Die pathologische Anatomie der Silikose und Silikotuberkulose

Tuberkulosenarzt

Pneumokoniose

Anthracosilicosis

J Am Med Assoc

Ischemic necrosis in anthracosilicosis

Arch Environ Health

Experimental infective pneumoconiosis with Mycobacterium tuberculosis (var. Muris) and hematite by inhalation and by injection

J Path Bact

Die Gewebswirkung von Quartz in Gegenwart von Eisenerzstäuben

Int Arch Gewerbepath Gewerbehyg

The relative toxicities of the main classes of minerals

The tissue reaction of the lungs of rats after the inhalation of coal dust containing 2% of quartz

Br J Ind Med

Inhalation studies of coal-quartz dust mixture

Ann N Y Acad Sci

Effect of kaolin on the lungs of rats

J Pathol Bact

Studies on the effect of quartz, bentonite and kaolin dust mixtures on rat lung

Experimental observations concerning the effects of mineral dust to pulmonary tissue

Med Lav

Diseases associated with exposure to silica and nonfibrous silicate minerals

Arch Pathol Lab Med

Diseases due to nonasbestos silicates

Tissue mineral identification

Analysis and interpretation of inorganic mineral particles in “lung” tissues

Thorax

Determination of microgram quantities of asbestos by X-ray diffractionChrysotile in thin dust layers of matrix material

Anal Chem

A new X-ray diffraction method for the quantitative analysis of free silica in airborne dust in working environment

Ind Health

Development and use of a pneumoconiosis database of human pulmonary inorganic particulate burden in over 400 lungs

Scanning Microsc

Electron microscope characteristics of inhaled chrysotile asbestos

Br J Ind Med

Identification of single asbestos fibers in human tissues

Evaluation of low-level asbestos exposure by transbronchial lung biopsy with analytical electron microscopy

J Electron Microsc

Treatment of mixed-dust pneumoconiosis with whole lung lavage

Am Rev Respir Dis

Non-fibrous inorganic particles in human bronchoalveolar lavage fluids

Scanning Microsc

Comparative analysis of inhaled particles contained in human bronchoalveolar lavage fluids, lung parenchyma and lymph nodes

Environ Health Perspect

Analytic methods for identifying and quantifying mineral particles in lung tissue

Non-fibrogenic (“inert”) minerals and pneumoconiosis

Original contributions
Proposed criteria for mixed-dust pneumoconiosis: Definition, descriptions, and guidelines for pathologic diagnosis and clinical correlation¹