Progressive massive fibrosis (PMF), characterized by the development of large conglomerate masses of dense fibrosis (usually in the upper lung zones), can complicate

silicosis Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis. Silic ...

and

coal worker's pneumoconiosis Coal workers' pneumoconiosis (CWP), also known as black lung disease or black lung, is an occupational type of pneumoconiosis caused by long-term exposure to coal dust. It is common in coal miners and others who work with coal. It is similar to bo ...

. Conglomerate masses may also occur in other pneumoconioses, such as talcosis,Chong S et al. Pneumoconiosis: Comparison of Imaging and Pathologic Findings. RadioGraphics, 2006;26:59-77.

berylliosis Berylliosis, or chronic beryllium disease (CBD), is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds, a form of beryllium poisoning. It is distinct from acute beryllium poisoning, wh ...

(CBD),

kaolin Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedra ...

pneumoconiosis,Glazer CS and Newman LS. Occupational Interstitial Lung Disease. Clinics Chest Med, 2004;25:467–478. and pneumoconiosis from carbon compounds, such as

carbon black Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid ...

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

, and

oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitut ...

. Conglomerate masses can also develop in

sarcoidosis Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly af ...

, but usually near the hilae and with surrounding paracicatricial emphysema. The disease arises firstly through the deposition of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

coal dust Coal dust is a fine powdered form of which is created by the crushing, grinding, or pulverizing of coal. Because of the brittle nature of coal, coal dust can be created during mining, transportation, or by mechanically handling coal. It is a form ...

(or other dust) within the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

, and then through the body's immunological reactions to the dust.

Presentation

According to the International Labour Office (ILO), PMF requires the presence of large opacity exceeding 1 cm (by x-ray). By pathology standards, the lesion in histologic section must exceed 2 cm to meet the definition of PMF.Craighead JE et al. Diseases Associated with Exposure to Silica and Nonfibrous Silicate Minerals. Arch Pathol Lab Med, 1988;112:673–720. In PMF, lesions most commonly occupy the upper lung zone, and are usually bilateral. The development of PMF is usually associated with a restrictive ventilatory defect on

pulmonary function testing Pulmonary function testing (PFT) is a complete evaluation of the respiratory system including patient history, physical examinations, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity ...

. PMF can be mistaken for

bronchogenic carcinoma Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, maligna ...

and vice versa. PMF lesions tend to grow very slowly, so any rapid changes in size, or development of cavitation, should prompt a search for either alternative cause or secondary disease.

Pathogenesis

The pathogenesis of PMF is complicated, but involves two main routes – an immunological route, and a mechanical route. Immunologically, disease is caused primarily through the activity of lung

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...

s, which phagocytose dust particles after their deposition. These macrophages seek to eliminate the dust particle through either the mucociliary mechanism, or through lymphatic vessels which drain the lungs. Macrophages also produce an inflammatory mediator known as

interleukin-1 The Interleukin-1 family (IL-1 family) is a group of 11 cytokines that plays a central role in the regulation of immune and inflammatory responses to infections or sterile insults. Discovery Discovery of these cytokines began with studies on t ...

(IL-1), which is part of the immune systems first line defenses against infecting particles. IL-1 is responsible for 'activation' of local vasculature, causing endothelial cells to express certain cell adhesion molecules, which help the cells of the body's immune system to migrate into tissues. Macrophages exposed to dust have been shown to have markedly decreased

chemotaxis Chemotaxis (from '' chemo-'' + '' taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemica ...

. Production of inflammatory mediators – and the tissue damage that ensues as an effect of this, as well as reduced motility of cells, is fundamental to the pathogenesis of pneumoconiosis and the accompanying inflammation, fibrosis, and

emphysema Emphysema, or pulmonary emphysema, is a lower respiratory tract disease, characterised by air-filled spaces ( pneumatoses) in the lungs, that can vary in size and may be very large. The spaces are caused by the breakdown of the walls of the alv ...

. There are also some mechanical factors involved in the pathogenesis of Complex Pneumoconiosis that should be considered. The most notable indications are the fact that the disease tends to develop in the upper lobe of the lung – especially on the right, and its common occurrence in taller individuals.

Diagnosis

Treatment

Incidence

Progressive massive fibrosis increased during the period 1970–2016 among coal miners in central Appalachia who filed for black lung benefits.

References

Occupational Lung Diseases, 3rd Edition, Morgan and Seaton https://web.archive.org/web/20060223051633/http://pim.medicine.dal.ca/il1.htm {{Respiratory pathology Lung disorders Occupational diseases