How are Polymyositis and dermatomyositis treated
What is the approach to treatment of Polymyositis and dermatomyositis ?
Poor prognostic features in PM/DM patients include severe weakness, dysphagia, respiratory muscle weakness, ILD, myocardial involvement, anti-SRP/anti-MDA-5/anti-155/140 antibodies, necrotizing myopathy on pathology, and malignancy. All patients need corticosteroids (CS) and immunosuppressive agents early.
CS are the mainstay of therapy for PM/DM. Commonly, prednisone is started at a dose of 1 to 1.5 mg/kg/day (up to 80 mg/day) in divided doses, and the dose is maintained until remission is achieved (improved strength and normalization of muscle enzymes), which usually takes 4 to 6 weeks. Taper by 20% each month until 20 mg/day, then by 5 mg a month to 10 mg/day. Once tapered to 10 mg/d, maintain that dose for 3 to 6 months before further taper. Intravenous pulse methyl-prednisolone is used for life-threatening disease (severe weakness or ILD). Subsequently, the dose is slowly tapered while monitoring for recurrence of disease activity. Most experts recommend combining CS with immunosuppressive agents from the onset of therapy to facilitate the steroid taper since over 50% fail CS alone.
Immunosuppressive agents are used early to help reduce the corticosteroid dose. Methotrexate (up to 25 mg/week orally or subcutaneously) or azathioprine (2–3 mg/kg/day) are used most often but can take up to several months to be maximally effective. Mycophenolate mofetil (MMF; 1–1.5 g twice a day [BID]) and leflunomide have also been used. MMF may be more effective for ILD and rash. Cyclophosphamide or combinations of immunosuppressive agents (methotrexate plus azathioprine) are used rarely but have been reported to be beneficial in refractory and life-threatening disease (anti-MDA5-associated ILD) and in JDM with vasculitis. Hydroxychloroquine and avoidance of the sun can be helpful adjuncts in treating the cutaneous manifestations of DM. In case series, tofacitinib shown effective for DM skin rash.
Tacrolimus (0.1 mg/kg/day; 2–5 mg BID) is effective in resistant T cell-mediated PM and lung disease (especially cryptogenic organizing pneumonia). Cyclosporine (3–5 mg/kg/day) has also been used with success, but tacrolimus seems to be better tolerated.
Intravenous immunoglobulin (2 g/kg over 5 days [0.4 g/kg/day] initially, followed by monthly 2 g/kg over 3 days) has been reported to be effective in severe, refractory DM especially in patients with dysphagia and those with anti-HMGCR disease. Although not Food and Drug Administration (FDA)-approved, most clinicians feel it also works in patients with PM.
Rituximab has recently been shown to be effective in DM patients and in PM patients with MSAs (anti-Jo-1, anti-Mi-2, anti-HMGCR, anti-SRP, others). Initial dose is 1 g on days 1 and 15 and then 1 g every 6 months.
Repository corticotropin injection (H.P. Acthar gel): this expensive medication is FDA-approved for treatment of DM/PM at a dose of 80 USP units subcutaneously twice a week for 3 months, then attempt to taper.
In the initial stages of disease, when muscle inflammation is most severe and when the patient is most weak, rehabilitation is recommended to be only passive/active-assisted range of motion exercises. After 4 to 6 weeks of medical therapy, as strength returns and muscle inflammation subsides, exercise for strengthening can slowly be added to the physical therapy regimen. All patients should receive appropriate vaccinations, osteoporosis and pneumocystis prophylaxis, and therapy to prevent aspiration pneumonia.