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

Silicosis, also known as Potter's rot, is a form of occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in forms of nodular lesions in the upper lobes of the lungs...

 and Coal worker's pneumoconiosis. Conglomerate masses may also occur in other pneumoconioses, such as talcosis

Talcosis

Pulmonary talcosis, less specifically referred to as talcosis, is a pulmonary disorder caused by talc.It has been related to silicosis resulting from inhalation of talc and silicates. It is also tied to heroin use where talc might be used as an adulterant to increase weight and street value. It is...

, berylliosis

Berylliosis

Berylliosis, or chronic beryllium disease , is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds. As an occupational lung disease, it is most classically associated with beryllium mining or manufacturing of fluorescent light bulbs...

 (CBD), kaolin pneumoconiosis, and pneumoconiosis from carbon compounds, such as carbon black

Carbon black

Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil. Carbon black is a form of amorphous carbon that has a high surface-area-to-volume ratio, although its...

, graphite

Graphite

The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

, and oil shale

Oil shale

Oil shale, an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen from which liquid hydrocarbons called shale oil can be produced...

. Conglomerate masses can also develop in Sarcoidosis

Sarcoidosis

Sarcoidosis , also called sarcoid, Besnier-Boeck disease or Besnier-Boeck-Schaumann disease, is a disease in which abnormal collections of chronic inflammatory cells form as nodules in multiple organs. The cause of sarcoidosis is unknown...

, but usually near the hilae and with surrounding paracitricial emphysema.

The disease arises firstly through the deposition of silica or coal dust

Coal dust

Coal dust is a fine powdered form of coal, 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.-Explosions:...

 (or other dust) within the lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

, 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. In PMF, lesions most commonly occupy the upper lung zone, and are usually bilateral. The development of PMF is usually associated with a restictive ventilatory defect on pulmonary function testing

Pulmonary function testing

Pulmonary Function Testing is a complete evaluation of the respiratory system including patient history, physical examinations, chest x-ray examinations, arterial blood gas analysis, and tests of pulmonary function. The primary purpose of pulmonary function testing is to identify the severity of...

. PMF can be mistaken for bronchogenic carcinoma 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 and causes

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

Macrophage

Macrophages are cells produced by the differentiation of monocytes in tissues. Human macrophages are about in diameter. Monocytes and macrophages are phagocytes. Macrophages function in both non-specific defense as well as help initiate specific defense mechanisms of vertebrate animals...

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 (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 bodies immune system to migrate into tissues. Macrophages exposed to dust have been shown to have markedly decreased chemotaxis

Chemotaxis

Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...

. 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

Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...

.

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.