Anti-synthetase syndrome is an
autoimmune disease
An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
associated with
interstitial lung disease,
dermatomyositis
Dermatomyositis (DM) is a long-term inflammatory disorder which affects skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may inc ...
, and
polymyositis
Polymyositis (PM) is a type of chronic inflammation of the muscles (inflammatory myopathy) related to dermatomyositis and inclusion body myositis. Its name means "inflammation of many muscles" ('' poly-'' + '' myos-'' + '' -itis''). The inflam ...
.
Signs and symptoms
As a
syndrome, this condition is poorly defined. Diagnostic criteria require one or more antisynthetase antibodies (which target
tRNA synthetase enzymes), and one or more of the following three clinical features: interstitial lung disease, inflammatory myopathy, and inflammatory polyarthritis affecting small joints symmetrically. Other supporting features may include fever,
Raynaud's phenomenon and "mechanics hands"-thick, cracked skin usually on the palms and radial surfaces of the digits.
The disease, rare as it is, is more prevalent in women than in men. Early diagnosis is difficult, and milder cases may not be detected. Also, interstitial lung disease may be the only manifestation of the disease. Severe disease may develop over time, with intermittent relapses.
Pathogenesis
It is postulated that autoantibodies are formed against aminoacyl-tRNA synthetases. The synthetases may be involved in recruiting antigen-presenting and inflammatory cells to the site of muscle or lung injury. The specific molecular pathway of the process awaits elucidation.
[
]
Antisynthetase antibodies
The most common antibody is "Anti-Jo-1" named after John P, a patient with polymyositis and interstitial lung disease detected in 1980. This anti- histidyl tRNA Synthetase antibody is commonly seen in patients with pulmonary manifestations of the syndrome.
The following are other possible antibodies that may be seen in association with antisynthetase syndrome: Anti-PL-7, Anti-PL-12, Anti-EJ, Anti-OJ, Anti-KS, Anti-Zo, Anti-Ha-YRS, and Anti-SRP.
Diagnosis
In the presence of suspicious symptoms a number of test are helpful in the diagnosis:[
* Muscle enzymes are often elevated, i.e. ]creatine kinase
Creatine kinase (CK), also known as creatine phosphokinase (CPK) or phosphocreatine kinase, is an enzyme () expressed by various tissues and cell types. CK catalyses the conversion of creatine and uses adenosine triphosphate (ATP) to create phosp ...
* Anti-Jo-1 antibody testing
* Electromyography
* Muscle biopsy
* Pulmonary function testing
* Lung biopsy
* Imaging such as High Resolution computed tomography [ANTISYNTHETASE SYNDROME AND ITS ASSOCIATION WITH INTERSTITIAL LUNG DISEASE-A CLINICAL AND RADIOLOGICAL REVIEW Naresh Kumar,Bhavya Basetti, Rajoo Ramachandran, Prabhu Radhan,Venkata Sai P.M. http://ijomcr.net/radiology/]
In certain situations, testing of other antibodies, specific imaging (MRI, thoracic high resolution computed tomography), and swallowing evaluation may be needed.
Treatment
Unfortunately, treatment for the anti-synthetase syndrome is limited, and usually involves immunosuppressive drugs such as glucocorticoids. For patients with pulmonary involvement, the most serious complication of this syndrome is pulmonary fibrosis
Pulmonary fibrosis is a condition in which the lungs become scarred over time. Symptoms include shortness of breath, a dry cough, feeling tired, weight loss, and nail clubbing. Complications may include pulmonary hypertension, respiratory failu ...
and subsequent pulmonary hypertension.
Additional treatment with azathioprine
Azathioprine (AZA), sold under the brand name Imuran, among others, is an immunosuppressive medication. It is used in rheumatoid arthritis, granulomatosis with polyangiitis, Crohn's disease, ulcerative colitis, and systemic lupus erythematosus, a ...
and/or methotrexate
Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...
may be required in advanced cases.[
]
Prognosis
Prognosis is largely determined by the extent of pulmonary damage.
References
External links
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, ICD10 = M35.8
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, Orphanet = 81
Rare syndromes
Syndromes affecting muscles
Rheumatology
Autoimmune diseases
Lung disorders
Syndromes affecting the lung
Syndromes affecting joints