Table 5.

Therapeutic regimens for PM/DM.

Patients condition	Agents	Typical dose	Side effect and toxicities
New-onset disease	Prednisone	1 mg per kilogram, up to 100 mg per day for 4–6 weeks (orally); taper to alternate days	Increased susceptibility to infection, osteoporosis, hypertension, diabetes, weight gain, steroid-induced myopathy, mood changes, skin fragility, avascular necrosis, glaucoma
Late or severe disease onset, rapidly worsening	Methylprednisolone	1000 mg per day for 3–5 days (IV), then switch to oral regimen
Steroid refractory	Intravenous Immunoglobulin	2 g/kg total dose given over 2–5 days (1 g/kg/day over 2 days or 0.4 g/kg/day over 5 days), repeated monthly for at least 3 months, intravenously	Flu-like symptoms, myalgias, fever, headache, fluid overload, rash, aseptic meningitis, caution in patients with cardiac conditions, risk of renal failure or thrombosis
Steroid-sparing regents	Azathioprine	2–3 mg/kg/day (orally)	Fever, abdominal pain, nausea, vomiting, anorexia; combination with allopurinol increased myelosuppression and hepatoxicity; thiopurine methyltransferase activity may need to be checked in certain patients prior to initiation of medication or in those with poor reaction to treatment
	Methotrexate	15–25 mg/week (orally), should be given with folate 1 mg/day (IV);	Hepatotoxicity, ILD (caution in those with anti- Jo-1 antibody positivity), interstitial pneumonitis, myelosuppression, renal toxicity, alopecia, stomatitis, oncogenicity, teratogenicity
	Mycophenolate mofetil	1–1.5 mg twice daily, 500 mg twice daily in renal impairment (orally)	Diarrhea, myelosuppression, tremors, hypertension
	Tacrolimus	2–3 mg twice daily (orally)	Increased susceptibility to infection, lymphoma, alopecia, skin erythema, pruritis, constipation, diarrhea, nausea, anemia, leukocytosis, thrombocytopenia, headache, hypertension, paresthesia, tremor, renal failure
	Cyclophosphamide	1–2 mg/kg/day (orally), or 1 g/m2 monthly （intramuscularly)	Gastrointestinal upset, alopecia, risk of malignancy, hemorrhagic cystitis, teratogenicity, sterility, increased risk of infection
	Cyclosporine	3–4 mg/kg/day (orally)in two divided doses, then increase up to 6 mg/kg/day	Hypertension, renal failure, gingival hyperplasia, Gastrointestinal upset, hypertrichosis, oncogenicity, tremor, risk of infection
Steroid refractory	Rituximab	1 g (IV), repeat in 2 weeks; then subsequent doses 6–9 months after second dose	Fever, nausea, infection susceptibility, rare infusion reactions, rare progressive multifocal leukoencephalopathy
No objective improvement	If diagnosis is reconfirmed, recommend participation in a research trial (candidates include eculizumab, alemtuzumab, tocilizumab (anti–IL-6), anti–IL-17, and anti– IL-1β and so on)

Modified from Refs. [4,5].