Proximal muscle weakness; Gottron papules, heliotrope, shawl sign
Confirm: ↑CK/AST + EMG → muscle biopsy (most accurate); anti-Jo-1
Treat: Prednisone 1 mg/kg + methotrexate/azathioprine; IVIG is a first-line add-on for dermatomyositis (ProDERM); risk-stratified cancer screen (IMACS 2023 — anti-TIF1γ/NXP2 → intensive screen incl. PET-CT)
Order set
- CK, AST/ALT
- EMG
- Muscle biopsy
- Myositis antibodies
- Malignancy screen
Criteria
AdmitDysphagia/aspiration or respiratory weakness
ICURespiratory failure / severe dysphagia
DischargeStrength improving, swallow safe, therapy + cancer screen
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Dysphagia/aspiration
- Respiratory muscle weakness
- Underlying cancer
- Anti-MDA5 → rapidly progressive ILD
Differentials
- Statin myopathy
- Hypothyroidism
- Inclusion body myositis
- MND
Common mistakes
- Missing associated malignancy/ILD
Disposition & follow-up
Steroids + steroid-sparing agent; age-appropriate cancer screen.
Discharge package
MedicationsSteroids + steroid-sparing agent
Follow-upRheumatology; cancer screen
Warning symptomsSwallowing/breathing difficulty, worsening weakness
💊 Treatment detail — doses & preparation
Prednisolonecorticosteroid
DoseMyositis: 1 mg/kg OD (max ~80 mg) then slow taper alongside steroid-sparing agent
Preparation5/25 mg tablets; gastro-resistant or plain with food
MonitorGlucose, BP, mood; bone protection if >3 mo (Ca²⁺/D ± bisphosphonate)
MethotrexateDMARD
Dose10–15 mg PO/SC once weekly, titrate to 20–25 mg weekly + folic acid 5 mg (different day)
Preparation2.5/10 mg tablets — WEEKLY, not daily (dispensing error kills); SC pens 7.5–25 mg
MonitorFBC, LFT, creatinine q2–4 wk until stable; avoid in pregnancy/liver disease
Azathioprinethiopurine immunosuppressant
Dose2–2.5 mg/kg OD (IBD, myositis, MG)
Preparation25/50 mg tablets with food
MonitorFBC + LFT weekly ×4 then q8–12 wk; TPMT before starting; avoid allopurinol combination
IVIGimmunoglobulin
DoseDermatomyositis: 2 g/kg IV over 2–5 d, monthly (ProDERM)
Preparation50/100 mL ready bottles; start slow (30 mL/h), escalate per tolerance
MonitorHeadache/aseptic meningitis, renal function, thrombosis; live vaccines after
📖 EULAR-ACR MyositisReviewed July 2026