Stem Cell Transplantation in Idiopathic Inflammatory Myopathy Diseases

Conditioning Regimen (In order to assure sterility testing, a minimum of 14 days will be required between stem cell collection and starting the conditioning regimen). The conditioning regimen is outlined in below: Cyclophosphamide 50 mg/kg/day will be given IV over 1 hour in 250 cc of normal saline on day -5, -4, -3, and -2. If actual weight is \< ideal weight, cyclophosphamide will be given based on actual weight. If actual weight is \> ideal weight, cyclophosphamide will be given as adjusted ideal weight. Adjusted ideal weight = ideal weight + 40% (actual weight minus ideal weight). Mesna 50mg/kg/day will be given IV over 24 hours in 250 cc of normal saline or D5W starting at 10AM each dose. Weight base is calculated same as cyclophosphamide as above. 1ATG (rabbit) 0.5 mg/kg on day -6 and 1mg/kg on day -5, -4, -3, -2 and -1 (total 5.5mg/kg, no dose adjustment) will be given IV over 10 hours in 250 cc of normal saline beginning at least 1 hour after infusion of cyclophosphamide. Premedicate with acetaminophen 650 mg po and diphenhydramine 25 mg po/IV 30 minutes before the infusion. Methylprednisolone- A suggested dose of 250mg IV should be administered 30 minutes before each ATG infusion. Hydration- A suggested rate of 125 cc/hr NS should be given starting 6 hours before the first cyclophosphamide dose and continued until 24 hours after the last cyclophosphamide dose. The rate of hydration will be aggressively adjusted. BID weights will be obtained. Amount of fluid can be modified based on patient's fluid status. Minimum target urine output is 2 liters/m2/day G-CSF 5 mcg/kg/day will be given subcutaneously and continued until the absolute neutrophil counts reaches at least 500/µl. Rituxan 500 mg will be given IV on the day before the first dose of ATG and the day after stem cell infusion.