Antisynthetase
Syndrome
Reliable, patient-centred information about ASyS — a rare systemic autoimmune condition caused by antibodies targeting aminoacyl-tRNA synthetase enzymes.
Educational content only · Not a substitute for medical advice
A systemic condition with a defining autoantibody
Antisynthetase syndrome (ASyS) is a rare autoimmune condition characterised by the presence of one or more autoantibodies directed against aminoacyl-tRNA synthetase (ARS) enzymes — proteins that attach amino acids to transfer RNA during protein synthesis.
The condition sits within the spectrum of idiopathic inflammatory myopathies (IIM) but is increasingly recognised as a distinct clinical entity. Its course is typically chronic and relapsing-remitting, requiring long-term immunosuppressive management.
Diagnosis is often delayed — on average by 1–3 years — due to its rarity and variable presentation across organ systems.
Most centres use the 2017 Connors criteria, which require a positive antisynthetase antibody plus one or more of: ILD, inflammatory myopathy, or arthritis.
You have new or worsening breathlessness, chest tightness, or unexplained proximal muscle weakness. Early ILD assessment significantly impacts outcomes.
Common manifestations
ASyS affects multiple organ systems. Presentation varies widely between individuals and antibody subtypes.
Interstitial Lung Disease
ILD is present in the majority of ASyS patients and is often the most life-limiting feature. Severity varies significantly by antibody subtype.
Inflammatory Myopathy
Proximal muscle weakness — difficulty climbing stairs, rising from a chair, or lifting arms — is a hallmark feature, especially in Jo-1 subtype.
Arthritis
Symmetrical inflammatory arthritis commonly affects the small joints of the hands and is frequently an early or presenting feature.
Mechanic's Hands
Rough, cracked, fissured skin on the lateral aspect of the fingers — named for its resemblance to the hands of a manual worker.
Raynaud's Phenomenon
Episodic vasospasm causing colour changes in the fingers in response to cold or stress. Common across all antibody subtypes.
Constitutional Symptoms
Fatigue, unexplained fever, and weight loss are common — particularly at diagnosis or during flares. Fatigue often persists even in remission.
Explore the antibody reference
Compare antibody subtypes by prevalence, key features, and symptomatic presentation — from Jo-1 to the rarer Zo and Ha subtypes.
View all antibodies →