It is good to hear that Emily is doing well. I hope that you have a good and really fun summer.
With respect to tapering in a somewhat sensitive situation, going from 20 g ever 4 weeks to 20 g every 4 weeks does seem kind of like a bigger step. I think of cumulative dose in 12 weeks which for 20 every 3 weeks is 80g and 20 g every 4 weeks is 60 g. I also think of the expected nadir IF IgG has a 28 day half life–which it doesn’t have for everyone–but the principle is the same for whatever it is. This is the nadir for 20 g every 3 weeks is somewhere in the 12 g-ish-supplemental in the body range and for 20 g every 3 weeks is expected to be in the 10 g supplemental in the body range (half of the added dose). I just cannot do calculus at this time of night to figure it out exactly, but it really does not matter. The important point is the both the total dose and the nadir is more with the 20 g every 3 weeks. There are several ways to make it a little gentler–one is to alternate every three weeks with every four weeks for a few times keeping the dose the same. Probably “safer” is to mildly INCREASE the dose to 25 g every 4 weeks. This makes the total dose in 12 weeks 75 g (slightly reduced from 80 g), but will keep the nadir in the 12 to 12.5 g supplemental in the body. Why do this? It is a slight reduction, it is simpler to come every 4 weeks and gentler on life, but most important the nadir is kept close to what it has been. For most of my kids, after I get them to every 4 weeks, we stay on that schedule and gently wean from there. It is less of a drop to go from 75 g in 12 weeks to 60 g in 12 weeks. For really sensitive kids, I have also alternated doses every 4 weeks as a baby-step reduction–for example, 25 g every four week alternating with 20 g every four weeks in order to have a gentler fall in total dose and in nadir level. I hope that this makes sense. I work with kids with a DIFFERENT autoimmune neurologic condition (opsoclonus myoclonus ataxia), but it is also one in which one has to be slow and gentle with tapering so that there is not a flair (with resultant further neurologic damage) and then need to start back at a much higher dose to get back to the same place.
WithHope for a cure of these diseases