What is your approach to using medications that can cause bone marrow suppression in SLE patients who have persistent leukopenia?

I am so glad someone asked this question. I have heard some peers state that they are reluctant to use immunosuppressants in this situation. 

However, I do not agree with this.

The whole reason our systemic lupus (SLE) patients have leukopenias is due to their autoimmunity (but make sure drugs, infection, etc did not contribute, of course). Theoretically, decreasing this autoimmunity with immunosuppressants may and should help.

I always place in my notes what my patient's nadir baseline counts (total WBC, absolute lymphocyte, and absolute neutrophil counts) were before being placed on any immunosuppressants. With our EHR, it is easy for this to then be carried over from note to note. As long as the WBC/ALC/ANC do not go significantly below those numbers on the immunosuppressant, then I feel comfortable continuing it.

Anecdotal case: A patient of mine with SLE and significant neutropenia complicated by recurrent boils while on hydroxychloroquine monotherapy developed class IV lupus nephritis (LN). I was nervous about treating her but had to, of course. After placing her on mycophenolate, her LN went into remission, her ANC improved significantly (off steroids), and she has not had any recurrence of boils over the past decade. 

I agree with @Dr. First Last’s approach. It helps to look for anti-neutrophil/granulocyte and anti-lymphocytes antibodies in some cases (some but not all labs offer this). The older method for testing this is to provide a 10-20 day trial of steroid with taper to see if the WBC count improves. Doses of prednisone equivalent 15-20 mg daily for 7-10 days should improve counts without inducing a dramatic neutrophil demarginization phenomenon. You will need to draw blood before and 1 week into the trial (That being said, if you have a neutrophil production problem, there will not be adequate neutrophils to demarginate…SLE should be a neutrophil destruction problem).

Generally, people are afraid of pushing Imuran, MTX, etc., if a patient with lupus has leukopenia. However, more often than not, the leukopenia is from the underlying autoimmune disorder, not from the drugs. Unless the WBC is extremely low, say 1,000 or so, I usually continue the DMARD. What matters is the absolute neutrophil count (ANC), and if it is over 500 or close to 1,000, then the patient will be fine.