It sounds like you might have Common Variable Immune Deficiency (CVID). Despite its name, CVID is not common, affecting about 1 in 25000 people. There is some information about it here http://primaryimmune.org/about-prima...ne-deficiency/.

CVID can lead to rheumatoid arthritis (seeing a rheumatologist could help here) and PN has been reported to be associated with it.

Your health care team should be able to advise you about this but IVIG is often effective in its management. IVIG is regular intra-venous infusion of pooled human antibodies