Siderosis

Place of siderosis in the pneumoconiosis group

Siderosis is a classic representative of metalloconioses — a broad group of occupational pneumoconioses whose development is directly associated with prolonged inhalation of industrial metal dust. In addition to siderosis, the most studied pathologies in this category include aluminosis and berylliosis. Titanosis, baritosis, stannosis, and a number of other lesions are also distinguished in clinical practice and pathological anatomy.

Etiology and occupational risk groups

The direct cause of siderosis development is the systematic exposure of the respiratory tract to iron-containing dust. The pathology has a clearly defined occupational nature. The main risk group includes workers in heavy industry and metalworking.

Among the professions most susceptible to this disease are:

• Miners specializing in the extraction of hematite (red iron ore, chemical formula $Fe_2O_3$).
• Foundry workers who regularly contact metal suspension.
• Specialists involved in polishing various metal products.
• Nail manufacturing workers.
• Metal engravers.
• Electric welders.

Pathogenesis features

Historically, the pathogenesis of siderosis was interpreted differently. Previously, the scientific community believed that iron dust itself was inert, and pulmonary tissue fibrosis was caused by an inevitable admixture of silicon dioxide. This condition was even given a separate name — silicosiderosis.

Currently, this theory has been revised. It has been reliably proven that iron-containing dust is capable of independently initiating pulmonary fibrosis, without the participation of silicon compounds.

A key feature of the course of siderosis is its prolonged and predominantly benign nature. The proliferation of connective tissue (fibrosis) is significantly less pronounced than in silicosis or silicatoses. The reason for such benignancy lies in the properties of the dust itself: iron particles are not toxic to living tissues and are fairly easily phagocytosed by macrophages, after which they are effectively removed from the body through the bronchial tree.

Macroscopic picture

During autopsy, the morphology of the lungs directly depends on the chemical composition of the dust that affected the patient. Traditionally, two main types of siderosis are distinguished:

1. Red siderosis. This form is caused by prolonged inhalation of dust containing iron oxides. Macroscopically, the lungs are noticeably increased in volume. The tissue of the organ acquires a specific yellowish-brown-red color.
2. Black siderosis. Develops upon contact with dust containing iron protoxide, as well as iron carbonates or phosphates. In this case, the lungs acquire a rich black color. Visually, this picture strongly resembles anthracosis (coal miner's pneumoconiosis).

Microscopic picture and lymph node changes

Histological examination of the lung tissue reveals mild interstitial sclerosis. Characteristic submiliary and miliary nodules are found in the parenchyma. They represent dense accumulations of macrophages (so-called "dust cells") whose cytoplasm is densely packed with fine particles of iron dust.

A few collagen fibers are determined between the accumulations of dust cells. To confirm the presence of iron in tissues, a special histochemical stain is used — Perls' reaction (Perls), which is always positive in siderosis.

The pathological process affects not only the lungs but also regional lymph nodes. A large amount of dust brought by macrophages accumulates in them, which is accompanied by the development of significant diffuse sclerosis of lymphoid tissue.

Class and exam questions

What else to study on this topic

• Place of siderosis in the classification of metalloconioses (aluminosis, berylliosis, titanosis).
• Mechanisms of non-toxic dust phagocytosis by pulmonary macrophages.
• Comparative morphology of interstitial sclerosis in various pneumoconioses.
• Pathogenesis of diffuse sclerosis in regional lymph nodes.

Other topics in the "Lung Diseases" section

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