Caplans syndrome overview

# Overview
Caplan syndrome is known as Rheumatoid pneumoconiosis. This is a combination of Rheumatoid Arthritis and pneumoconiosis. It is a rare syndrome occurring mostly in miners exposed to silica, coal and asbestos. For the first time, Caplan, a British physician in 1953 first described this syndrome. It is hypothesized that silica get ingested by macrophages. Silica destroys the macrophages and again engulfed by another macrophage. This repeating process leads to chronic inflammation and fibrosis. Due to having the capability to move around, silica can  travel to other organs away from lung and can induce autoantigens. Silica has an adjuvant effect on antibody production. In patients with silicosis , increased rheumatoid factor and antinuclear antibodies has been found. By producing TNF- and Interleukin 1 , silica induces joint destruction. Silica also plays a role in inducing both innate and adaptive immunity. Patients with Caplan syndrome are mostly asymptomatic but in advanced stages dyspnea and cough might occur. In Caplan syndrome, increased inflammatory markers are found in serum study though there is no arthritis. Caplan syndrome with polyarthritis mostly positive for Anti citrullinated Peptide Antibodies (ACPA). Caplan nodules can appear with or before the onset of arthritis. In many cases miners have typical radiographic pictures of Caplan syndrome without any features of Rheumatoid Arthritis. Chest X ray findings of Caplan syndrome is characterized by well defined lung nodules of 0.5-5 cm throughout the lungs but predominantly in the peripheral areas. These nodules might appear as crops and later coalesce into a larger one. The onset of nodules are sudden, rapidly growing and can remain in the lungs for years longer. They might regress spontaneously unless get cavitated or calcified. Pleural effusion and pneumothorax are rare complications. CT scan findings are similar to chest x ray but provides more specific information such as mixed nodular infiltrative changes in lungs. But chest x ray or CT scan are not capable of differentiate between Caplan nodules and ordinary silicotic nodules. Biopsy is required to confirm the diagnosis. On histopathology, Caplan nodules show central necrosis similar to rheumatoid nodules except the presence of dust particles. Surrounding the dust ring there is a zone of inflammation consisting of granulocytes, macrophages and giant cells. This inflammatory zone is the distinguishable criteria of Caplan nodules from rheumatoid nodules. There is no definitive treatment for Caplan syndrome. Lung nodules in Caplan syndrome usually do not require any treatment until any complication develop. Disease modifying anti rheumatic drugs (DMARDs) can be used to treat Rheumatoid arthritis. But DMARDs have no role in treatment of pulmonary nodules. In some cases, corticosteroid found to be helpful to stop the progression of pulmonary nodules. Anti TNF therapy are commonly used in treatment of RA but recent study showed that Anti TNF therapy may induce pulmonary nodules. Anti TNF therapy play role in activating latent tuberculosis and silicosis increase the risk of tuberculosis infection . So, it is strongly recommended to screen for latent TB in the patients with Rheumatoid Pneumoconiosis. In irreversible pulmonary fibrosis lung transplant can be the ultimate choice.

# Historical perspective
In 1953, the chest x ray findings of multiple pulmonary nodules, in the coal miners with Rheumatoid Arthritis(RA) of Welsh, was described by Caplan. In 1940 and 1955, rheumatoid nodules were described in autopsy study of heart and lungs. An epidemiological study was conducted by Miall and associates in 1955 to determine the validity of Caplan syndrome. J. Gough reported the histological diagnostic findings for Caplan Syndrome in 1958.

# Pathophysiology
Caplan Syndrome is known as Rheumatoid pneumoconiosis. In patients with rheumatoid arthritis, lungs show increased immune response to the foreign materials. In coal miners with RA, exposure to silica causes the release of different cytokines as interleukin-1,granulocyte colony stimulating factor and tumor necrosis factor-alpha by monocytes and macrophages. Lymphocytes get activated by the cytokines and leading to hyperactive autoimmune response.

# Causes
Caplan syndrome is caused by breathing in coal mining dust. This causes inflammation and can lead to the development of many small lung lumps (nodules) and mild asthma-like airway disease. The condition occurs in miners (especially those working in anthracite coal-mines), asbestosis, silicosis and other pneumoconioses. There is probably also a genetic predisposition and smoking is thought to be an aggravating factor.

# Caplans syndrome differential diagnosis
Caplan syndrome must be differentiated from Asbestosis, Silicosis, and Tuberculsosis.

# Epidemiology and demographics
The incidence of Caplan syndrome is 1 in 100,000 people but it is decreasing due to the reduction of exposure to coal, silica, and asbestos. Silica exposure has the most prevalence of Caplan syndrome.

# Risk factors
Common risk factors in the development of Caplan syndrome include pneumoconiosis, rheumatoid arthritis.

# Natural History, Complications and Prognosis
The patients with Caplan syndrome are mostly asymptomatic initially. Lung nodules in Caplan syndrome are rapidly growing; gain final size within weeks to month and then remain unchanged for years long. If left untreated, patients with Caplan syndrome may progress to develop wheeze in the chest which doesn't change with cough suggestive of irreversible pulmonary fibrosis

# Diagnosis

## History and Symptoms
Caplan Syndrome is mostly common in coal miners with Rheumatoid Arthritis. Presenting symptoms could be shortness of breath, cough, wheezing.

## Physical Examination
Common physical examination findings of Caplan Syndrome include typical Rheumatoid arthritis features as swollen, tender metacarpophalangeal and proximal interphalangeal joints. Pulmonary findings might include wheeze, crackles not improving with coughing.

## Laboratory Findings
No definitive laboratory findings are related to Caplan syndrome. But serum study might show positive findings of Rheumatoid factor, antinuclear antibodies.

## X-ray
An x-ray may be helpful in the diagnosis of Caplan Syndrome. Findings on an x-ray suggestive of Caplan Syndrome include well defined round , cavitating nodules with the diameter of 0.5-5cm.

## CT scan
There are no certain chest CT scan findings than the chest x-ray associated with Caplan Syndrome.

## MRI
There are no MRI findings associated with Caplan Syndrome.

## Other Imaging Findings
There are some imaging findings of hands and feet such as bilateral erosion of bones and joint space narrowing which are associated with Caplan Syndrome.

## Other diagnostic studies
Serum study may be helpful in the diagnosis of Caplan Syndrome. Serum study may found positive for rheumatoid factor, antinuclear antibodies, elevated ESR, and CRP.

# Treatment

## Medical Therapy
There is no treatment for Caplan Syndrome; the mainstay of therapy is supportive care.
Supportive therapy for Caplan Syndrome includes treatment of Rheumatoid arthritis, Steroid. Lung transplant for irreversible pulmonary fibrosis..

## Surgery
No definitive surgery is helpful in Caplan Syndrome except in massive pulmonary fibrosis, lung transplant is required.

## Primary Prevention
The primary preventive measure for Caplan syndrome is reducing exposure to inorganic dust as silica, asbestos.

## Secondary Prevention
Effective measures for the secondary prevention of Caplan's syndrome include limited exposure to respirable mine dust, personal respirable dust monitor can be used by the miners to monitor dust in their breathing zones, a regular medical screening to detect pneumoconiosis in the early stages, smoking cessation, and medical counseling.