Synopsis
Recognise antisynthetase syndrome when interstitial lung disease, myositis, arthritis and characteristic skin or vascular clues cluster, interpret antibody testing carefully, and treat lung-threatening disease with coordinated early combination immunosuppression.
- Suspect antisynthetase syndrome when ILD clusters with inflammatory myopathy, non-erosive arthritis, Raynaud phenomenon, fever or hyperkeratotic fissured mechanic hands.
- A patient need not show the full classic triad at presentation; lung disease may precede weakness and CK may remain normal, especially with non-Jo-1 antibodies.
- Request an experienced myositis antibody panel when phenotype supports it and confirm surprising line-blot results because low-level isolated reactivity can be false.
- At baseline obtain HRCT, spirometry, lung volumes and DLCO, oxygen assessment, CK and muscle function, ECG, echocardiographic risk assessment and swallowing review when indicated.
- NSIP, organising pneumonia and mixed NSIP-organising patterns are common; HRCT pattern helps but does not distinguish immune activity from infection without clinical and microbiological synthesis.
- For rapidly progressive ILD, admit and treat infection as a parallel possibility while using high-dose glucocorticoid plus an early specialist steroid-sparing agent rather than glucocorticoid alone.
- Mycophenolate, tacrolimus, rituximab or cyclophosphamide are selected according to severity, prior treatment, kidney and liver function, infection and reproductive factors; much use is specialist and off-label.
- Monitor FVC, DLCO, oxygen need, HRCT trajectory, strength, CK and swallowing separately; improved CK does not prove the lungs are controlled.
- Provide Pneumocystis prophylaxis when the immunosuppressive combination and local risk threshold indicate it, and screen TB, hepatitis and vaccines before biologic therapy when time allows.
- Plan pregnancy during stable disease on compatible treatment; mycophenolate, methotrexate and cyclophosphamide require pre-conception substitution, while tacrolimus and azathioprine may be compatible under specialist guidance.
Key red flags
Rapidly worsening dyspnoea, resting hypoxia, falling FVC or diffuse new HRCT change requires same-day assessment for ILD progression and infection.
Dysphagia, weak cough, low supine FVC or hypercapnia suggests bulbar or respiratory muscle involvement in addition to parenchymal lung disease.
Fever, neutropenia, oral candidiasis or new focal opacity during combined immunosuppression requires urgent opportunistic-infection assessment.
Chest pain, syncope, troponin rise or disproportionate DLCO loss requires evaluation for myocarditis, pulmonary embolism or pulmonary hypertension.
A hot joint with systemic illness needs aspiration and culture; inflammatory arthritis does not protect against septic arthritis.
Increasing oxygen need and bilateral ground-glass or organising change over days to weeks is an emergency despite modest CK or muscle findings.
Wet voice, choking, weak cough, orthopnoea or low supine vital capacity identifies aspiration and ventilatory risk beyond parenchymal ILD.
Investigation priorities
Identify an antisynthetase specificity and associated risk phenotype within compatible clinical disease.
Management branches
Unexplained ILD or myositis accompanies mechanic hands, arthritis, Raynaud or fever.
- Document onset and tempo, occupational and medicine exposures, full skin and joint examination, objective strength, swallowing, cough and respiratory physiology.
- Request HRCT, PFT or DLCO, muscle enzymes and phenotype-led myositis antibodies, confirming discordant serology with the laboratory.
- Discuss lung imaging and pathology in an ILD-myositis multidisciplinary service and use MRI, EMG, biopsy or bronchoscopy for unresolved mechanism.
Clinically meaningful ILD, myositis or arthritis is active without immediate respiratory failure.
- Start an appropriate oral glucocorticoid dose and introduce mycophenolate, tacrolimus, azathioprine or another specialist agent early to reduce cumulative exposure.
- Treat arthritis, Raynaud, reflux and aspiration separately and begin graded muscle and pulmonary rehabilitation once inflammation is stabilising.
- Set serial FVC, DLCO, oxygen, strength, CK and swallowing targets and taper only when the threatened organ remains controlled.