Your child has a high Mycoplasma IgG and a negative IgM. One doctor says "past infection, ignore it." Another wants to treat. Here is why they disagree, and how to get a real answer.
IgM = recent or acute. It rises about a week after infection, peaks around three to six weeks, then fades. It is the "this is happening right now" marker.
IgG = you have met it. It rises later and can stay elevated for years. A single high IgG tells you your child encountered Mycoplasma at some point. It does not, by itself, tell you it is active today.
A standard infectious-disease doctor will usually read high IgG with negative IgM as past infection, no treatment.
A PANS-literate or chronic-infection doctor is often more willing to treat on IgG plus the clinical picture — because Mycoplasma is an intracellular organism that can persist, and in a persistent or reactivated infection children frequently do not re-mount an IgM response.
A high IgG on its own is not a reason to treat — but it is a reason to look further rather than dismiss it. If the clinical picture fits, ask for the PCR and a repeat IgG and you will have an answer instead of a maybe.
Worth knowing: azithromycin covers Mycoplasma, also covers strep, and is independently anti-inflammatory. In a child with both histories, one drug can address several things at once — a useful conversation with whoever prescribes.
Want this answered for your own child? A Plan B synthesis reads every lab and note you have — together — and tells you what is driving the picture, what has never been checked, and what to ask for next.
The first one is free, and you keep the list either way. Phone photos of labs are fine.
Plan B for PANS is written by a parent, not a physician. Nothing here is medical advice or a substitute for your child's clinicians — it is meant to make you the best-informed person in the room when you talk to them.