• INCLUSION CRITERIA:

Ability and willingness to provide informed consent (adults greater than or equal to 18 years) or assent (children greater than or equal to 13 years) to all aspects of the study after full information is provided.

Nephrotic range proteinuria that persists for at least 3 months.

Nephrotic range proteinuria that persists despite angiotensin antagonist therapy (ACE inhibitor or ARB) for at least on month, unless intolerant. If patients have not started ACE inhibitor therapy before they are referred to NIH, we plan to start lisinopril 5 mg daily. We will advance the dose of ACE inhibitor as tolerated. Nephrotic range proteinuria, defined as 24 hour urine protein excretion greater than or equal to 3.5 g/d, must be documented in at least two 24 hour urine collections obtained during the month prior to initiating sirolimus. Incomplete urine collections (based on inadequate creatinine excretion) will be excluded.

Renal biopsy must reveal typical changes of membranous nephropathy by light and electron microscopy.

SLE as defined by the presence of at least 4 criteria established by the American Rheumatism Association (Lupus Membranous Nephropathy) or no evidence of a secondary form of membranous nephropathy (Idiopathic Membranous Nephropathy).

EXCLUSION CRITERIA:

Intolerance to sirolimus or prior use of sirolimus for membranous nephropathy.

Estimated GFR less than 30 mL/min/1.73(2) (determined by the 5 variable version of the MDRD Study prediction equation).

Immunosuppressive medications or experimental medications of any type during the two-month period prior to initiating sirolimus, with the following two exceptions:

First, patients with lupus membranous nephropathy are permitted to have received modest doses of corticosteroids (no more than the equivalent of prednisone 10mg/day) for control of extra-renal manifestations of SLE during the two-month period prior to starting sirolimus treatment.

Second, patients with worsening nephrotic syndrome (urine protein excretion rate doubles +/or serum albumin decreases by greater than or equal to 1.0 g/ dL to less than 2.5 g/dL on at least 2 determinations during or following a previous immunosuppressive treatment) should fulfill the following criteria:

a) should be off prednisone for at least 2 weeks before performing the baseline evaluation and starting sirolimus (if the patient has idiopathic membranous nephropathy): b) should be on low-dose corticosteroids (no more than the equivalent of prednisone 10 mg/day) for at least 2 weeks before performing the baseline evaluation and starting sirolimus (if the patient lupus membranous nephropathy); c) should be off cyclosporine for at least 2 weeks before performing the baseline evaluation and starting sirolimus; d) should be off cyclophosphamide, chlorambucil, azathioprine and mycophenolate mofetil for at least 4 weeks before performing the baseline evaluation and starting sirolimus;

Children less than 13.0 years.

Active acute or chronic infection requiring antimicrobial therapy or serious viral infection (e.g. HIV, hepatitis, herpes zoster). Patients with a reactive PPD must have completed a 6 to 12 month course of isoniazid as recommended by an infectious disease consultant. Patients with a non-reactive PPD and non-reactive anergy panel must complete a 6 to 12 month course of isoniazid if recommended by an infectious disease consultant.

Pregnant women, nursing mothers or individuals (men and women) not practicing birth control.

Uncontrolled hypertension, defined as BP greater than 140/90 on greater than 25% of measurements. Blood pressures will be measured 3 times at each clinic visit after the patient has sat quietly for at least 5 minutes. Thus at least 6 BP determinations will be recorded prior to initiating sirolimus therapy.

Chronic liver disease sufficiently severe to impair sirolimus metabolism; this would include prolonged pro-thrombin time. Patients with abnormal liver function tests will be evaluated by the Hepatology Consult Service to determine whether protocol participation is appropriate.

Basal thrombocytopenia less than 100,000 cells/microliters or absolute neutrophil count less than 2000 cells/microliters or hematocrit less than 30.

Cancer diagnosis or cancer recurrence within the preceding 5 years, excluding basal cell carcinoma of the skin.

Routine use of NSAIDS, defined as NSAID use more than two doses a week.

Clinically significant medical conditions, which in the opinion of the investigators, could increase the subject's risk of participating in the study or could confound the interpretation of the results of the study.