CD79A and stiff-person syndrome: Possible reasons that SCIg is better tolerated than IVIG include slower rate of systemic exposure/absorption of immunoglobulin, different escalating dosing regimens, difference in pharmaceutical properties (e.g., stabilizer, pH, sodium content, osmolality, IgA content), shorter infusion times, etc. Furthermore, the reported improvement of SPS symptoms in some patients after transitioning to SCIg may be attributed to the lower side effect profile compared to IVIG, as pain and stress can exacerbate SPS symptoms.