Caplan syndrome is a pathology characterized by the development of primary chronic arthritis against the background of progressive pneumoconiosis. The clinical picture consists of symptoms of general intoxication, shortness of breath, dry cough and joint damage resembling rheumatoid arthritis (symmetrical aching pains, morning stiffness). The diagnosis is established on the basis of professional anamnesis, detection of a high titer of rheumatoid factor in the blood, radiological changes. A comprehensive approach is used for treatment – cessation of contact with industrial dust, bronchodilators, anti-inflammatory drugs.
Caplan syndrome (Caplan-Coline syndrome, silicoarthritis, rheumatoid pneumoconiosis) is a complication of occupational pulmonary disease – pneumoconiosis. The disease was first described in 1953 by the English physician E. Caplan, who discovered the relationship of progressive polyarthritis with work in coal mines and the occurrence of pneumoconiosis. Pathology affects mainly men aged 40-55 years. According to statistics, the attachment of joint lesions occurs in about 0.1-0.6% of cases of silicosis.
Causes of Caplan syndrome
The occurrence of Caplan syndrome is caused by prolonged exposure to industrial dust containing silicon oxide on the human body. Miners, workers of foundries, machine-building, metalworking and ceramic industries are constantly in contact with this substance. People of these professions are at an increased risk of silicosis. The exact cause of arthritis in pneumoconiosis has not been established.
The mechanism of pulmonary disorders in Caplan syndrome is well studied. Fine dust particles entering the respiratory system together with air are deposited on the mucous membrane of the small bronchi and alveoli. Then they undergo phagocytosis by alveolar macrophages. Silicon dioxide damages the cytoplasm, causes mitochondrial degeneration and increased membrane permeability.
As a result of incomplete phagocytosis, under-oxidized compounds (alpha-ketoglutarate) accumulate, which have a stimulating effect on the enzymes involved in collagen synthesis. This leads to the proliferation of collagen fibers in the lungs – fibrosis. Pathoanatomic examination of fibrous areas of the lungs reveals necrotic collagen fibrils surrounded by phagocytes and polymorphonuclear leukocytes, epithelioid cells.
The pathogenesis of arthropathy is based on immunological disorders. It is assumed that macrophages that have absorbed silicon particles begin to secrete various cytokines and inflammatory mediators: interleukin-1, interleukin-6, tumor necrosis factor. This triggers an immune autoaggression reaction, including the production of rheumatoid factor.
Caplan syndrome symptoms
The disease is characterized by a gradual slow manifestation. At the initial stage, an asymptomatic course is often observed. There may be slight difficulty breathing during intense physical exertion, moderate stabbing pains in the chest without a clear localization, periodic dry unproductive cough. With an increase in the duration of exposure to silicon particles on the lung tissue, the symptoms become more pronounced.
Shortness of breath worries with little physical activity or even at rest. There is a constant debilitating cough. Chest pains are getting worse. Possible attacks of suffocation. In the future, emphysema of the lungs is formed, the chest takes a barrel shape. Due to developing respiratory failure, signs of general hypoxia are added: dizziness, a bluish tinge of the lips, nose and fingertips. For Caplan syndrome, a wave-like course with periods of exacerbations and remissions is typical.
Many patients suffer from manifestations of general intoxication: fatigue, subfebrile fever, sweating. From the onset of the disease to joint damage, it may take several months or even years. Arthropathy does not differ from that of rheumatoid arthritis. More often, small joints of the hands (metacarpophalangeal, proximal interphalangeal) are involved in the pathological process.
Morning stiffness is characteristic, aching pains that decrease after physical activity. The peak of the pain syndrome is observed in the morning. The joints are swollen, the skin above them is hyperemic. As the disease progresses, deformities develop, movements are significantly limited. Of the large joints, knee, ankle, shoulder joints are more often affected. In some patients, rheumatoid nodules can be found – subcutaneous painless formations up to 3-5 cm in diameter.
Caplan syndrome often leads to disability and disability. Due to the severe deformity of the joints caused by arthritis, the patient becomes unable to self-care. Diffuse pulmonary fibrosis provokes life-threatening complications such as pulmonary hypertension and right ventricular heart failure. According to some reports, patients with Caplan syndrome have an increased risk (about 30 times) of infection with Mycobacterium tuberculosis.
Cavities formed in the lung tissue can be inflated (abscess). More rare complications include lung cancer, spontaneous pneumothorax. As a result of immunological disorders in silicosis, it is possible to develop other autoimmune pathologies from the group of systemic connective tissue diseases, in particular, systemic scleroderma.
Patients with Caplan syndrome should be under the supervision of a pulmonologist, a occupational pathologist and a rheumatologist. A significant role in the diagnosis is played by professional anamnesis. During a general examination, attention is paid to the barrel-shaped shape of the chest, box percussion sound, weakened or hard breathing. To clarify the diagnosis, an additional examination is prescribed, including:
- Laboratory tests. In the general blood test, inflammatory markers are detected – leukocytosis, an increase in ESR. Compensatory erythrocytosis and an increase in hemoglobin concentration are possible. The most specific laboratory indicator is considered to be a very high titer of rheumatoid factor. In the advanced stage, the analysis of blood gases determines an increased partial pressure of carbon dioxide (PaCO2) and a reduced partial pressure of oxygen (PaO2).
- X-ray or CT. On an X-ray or computed tomogram, rounded darkenings of small sizes are visible, mainly in the peripheral parts of the lungs. Enlarged root and mediastinal lymph nodes are often detected. Thickening of pleural leaves is possible.
- Spirometry. When measuring the function of external respiration, there is a restriction or mixed type of violation – a decrease in the vital capacity of the lungs, the residual volume and the volume of forced exhalation.
- Joint x-ray. The image of the affected joints shows periarticular osteoporosis, narrowing of the articular gaps, multiple erosive defects.
Differential diagnosis is carried out with diseases that are manifested by a combination of respiratory symptoms and joint syndrome. Such diseases include sarcoidosis, langerhans cell histiocytosis, systemic vasculitis (granulomatosis with polyangiitis, nodular periarteritis, Churge-Strauss syndrome).
Caplan syndrome treatment
Depending on the severity of the patient’s condition, treatment is carried out on an outpatient basis or in a multidisciplinary hospital. Currently, there are no effective methods to achieve a complete cure of the disease. All measures are aimed at slowing the progression of the pathological process, relieving symptoms and preventing the development of complications.
The determining condition for successful therapy is the cessation or maximum restriction of contact with dust containing silicon dioxide. This implies a change in the working regime or the sphere of professional activity. Among other non-drug methods of treatment, it is worth highlighting smoking cessation, physical therapy and respiratory gymnastics. The schemes of conservative therapy of Caplan syndrome do not differ from those for pneumoconiosis and rheumatoid arthritis:
- Antifibrotic agents. To influence the main link of pathogenesis, a drug is prescribed that suppresses the growth of connective tissue.
- Bronchodilators. Since bronchial obstruction often occurs in pneumoconiosis, inhalers with beta-adrenomimetics are used to relieve spasm and edema. Prolonged medications in combination with glucocorticosteroids are suitable for continuous use, fast–acting ones are suitable for cupping.
- Mucolytics. To dilute the viscous mucus that accumulates in the bronchi, acetylcysteine is prescribed. This medication also has an antioxidant effect. Preferably use via a nebulizer.
- Oxygen therapy. In the presence of clinical signs of severe respiratory failure and laboratory confirmation of general hypoxia (PaO2 below 55 mmHg), oxygen inhalation through a mask or nasal cannula is recommended.
- Systemic anti-inflammatory drugs. NSAIDs are used to relieve joint pain. Glucocorticosteroids, cytostatics, monoclonal antibodies are used as basic therapy that slows down the destruction of joints.
With the development of terminal respiratory failure, the preservation of pronounced hypoxemia against the background of constant inhalation of oxygen to preserve life, lung transplantation is indicated. With advanced arthritis, which causes severe deformation and significant restriction of movement in the joints, operations such as arthroscopic synovectomy and joint replacement are performed.
Prognosis and prevention
Caplan syndrome is a rare complication of pneumoconiosis with a high percentage of disability. The main causes of death are severe respiratory failure and pulmonary heart disease. The prognosis directly depends on timely diagnosis, so regular medical examinations play an essential role.
The main preventive measures to reduce the impact of silicon dust are carried out at the workplace. These include sealing the technological process, adequate ventilation equipment, wearing respirators. Infectious diseases of the respiratory system can provoke an exacerbation. To prevent them, patients are vaccinated against influenza and pneumococcal infection.
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