The purpose of this study is to determine whether calcitriol is effective in the treatment of lupus nephritis.

Systemic lupus erythematosus (SLE) is an autoimmune disease and renal involvement represent one of the most common manifestations of it . On the other hand, there is evidence that vitamin D and its analogs have known immunosuppressant properties and profound effects on glomerular mesangial cell proliferation. Moreover much literature such as animal studies suggests it as a therapeutic intervention in autoimmune disease. The investigators plan to conduct a double blind randomized control clinical trial to study effects of calcitriol on progress and activity of lupus nephritis. Fifty patients with clinically quiescent SLE and biopsy-proven glomerulonephritis will be recruited. They will be treated with calcitriol for 1 year. Proteinuria, renal function, lupus disease activity, serum inflammatory markers will be monitored.

Inclusion Criteria:

• Aged 18-65 years
• Baseline Systemic Lupus Erythematosus Disease Activity Index score <= 4
• Estimated glomerular filtration rate more than 15 ml/min/1.73m2
• Proteinuria > 1 g/day (or proteinuria > 1 g/g-Cr) in 2 consecutive samples within 12 weeks despite ACE inhibitor at least 3 months
• On maintenance dose of prednisolone < 15 mg/day with or without other immunosuppressive medications
• Serum calcium level in normal range( 8.5-10.5 mg/dl)
• History of biopsy-proven lupus nephritis clinical quiescent SLE for at least 3 month
• Willingness to give written consent and comply with the study protocol

Exclusion Criteria:

• Pregnancy, lactating or childbearing potential without effective method of birth control
• Severe gastrointestinal disorders that interfere with their ability to receive or absorb oral medication
• History of malignancy, including leukemia and lymphoma within the past 2 years; Systemic infection requiring therapy at study entry
• Any other severe coexisting disease such as, but not limited to, chronic liver disease, myocardial infarction, cerebrovascular accident, malignant hypertension
• History of drug or alcohol abuse within past 2 years
• Vitamin D deficiency(25 hydroxy vitamin D less than 20ng/ml)
• Participation in any previous trial on vitamin D analogue
• Patients receiving treatment of vitamin D and/or its analogue for other medical reasons within the past 4 weeks
• Patients who are taking multivitamin supplement that contains vitamin D could be enrolled after 4 weeks of wash out period by changing to a preparation that has no vitamin D
• On other investigational drugs within last 30 days
• History of a psychological illness or condition such as to interfere with the patient's ability to understand the requirement of the study
• History of non-compliance; Known history of sensitivity or allergy to vitamin D analogs