This depends on the type of CVID, its genetic basis and the health problems, past and present that the person may have.  CVID is probably a collection of multiple genetic disorders with sufficient common features for them to be given the same umbrella diagnostic label.  From our current understanding, some immune deficiency is caused by genetic changes that only affect the immune system, but in other disorders, the driver behind many of the symptoms of the disease may be in non-immune cells with the same genetic abnormality.  When the disorder is restricted to the immune system and the symptoms are severe enough, it may be appropriate to consider BMT.  When the disorder affects cells in other tissues and organs and more widely, or we just don’t know, the risks of the BMT may not be met with an improvement in the overall clinical condition.  Except for very severe cases, more like combined immune deficiency (CID) or where a patient has one or more lymphomas and has CVID, at present the approach in general is to pursue a genetic diagnosis, and when there isn’t one, to consider non-BMT options.