IgM positive but IgG negative

HI everyone,
I have been having some weird symptoms such as vertigo, tinnitus, weird vision, eye floaters, feelings of kind of tingling in different parts of my body, headaches and neck pain, sensitivity to light and the list goes on and on.

I recently had a lyme test done and the western blot came back IgM positive but the IgG was negative. Is it possible this is a false positive? Have any of you had positive IgM but negative IgG and have had symptoms for at least 8 months??

thanks so much

[JackieCalifornia]

IgM measures a more recent infection; IgG measures an older infection.  Therefore if you have a positive IgM and negative IgG, it probably means you are more recently infected.  There is not an absolute date cut off for when IgG fades and IgM increases, that I am aware of.  Of more importance to your MD should be your physical symptoms and the fact that you are positive on the test.  

Does your test just say "positive" and "negative" without any detail?  If so, it's not one a Lyme MD would likely use, because the IGeneX lab runs tests that have more detail.  I have heard people posting here who gripe about IGeneX, but I don't know why.  In medicine there are few things that are black and white -- it's all shades of grey.

[jackiem81]

thanks Jackie... so IgM measures recent infection and IgG measures an older infection. Then you said there is no cute off date for when IgG fades and IgM increases so after a while the IgG fades and the IgM increases again? Or did you mean that the IgM fades and changes to IgG?? sorry I am confused

[JackieCalifornia]

We're at the limits of my knowledge about immunoglobulins.  As far as I know, it's a general indicator of the relative age of the infection.  Someone else here might be able to explain better.  

(Wikipedia has an interesting but very intense article on immunoglobulins, of which there are several types that kick in at different times.  IgG [immunoglobulin G] and IgM [immunoglobulin M] are two that are tracked in a Lyme infection to give an idea of how old the infection is, since all blood tests for Lyme rely not on finding the Lyme bacteria in the blood, but instead rely on finding the body's reaction (immunoglobulins) to the bacteria.  

I think of it as being able to map the high-crime areas of town not by counting criminals [because you can't tell by looking at someone whether s/he is a criminal], but by counting the police cars.  The more police, maybe the worse the area of town.  A rough analogy, but the only one I can come up with currently.

Why different stages of infection cause the body to produce different varieties of immunoglobulins, I don't know.  

What my LLMD does is track the progress of disease and treatment over time by ordering periodic blood tests to measure the immunoglobulin response and other blood markers.  Different people have stronger or weaker immune systems from other people; for example my LLMD tells me I have a strong immune system given the big response it produces against the bacteria.

After a while, the body can get tired of fighting and gets used to the bacteria being around, so the immune response fades, I've read (I think).  Sometimes the MD will give a short course of antibiotics, which causes the immune system to reactivate against the Lyme and give a more positive blood test, which measure the antibodies and not the Lyme bacteria.  It's called an 'antibiotic challenge.'

Everybody's immune system is different, and very ill people may not mount a strong immune response, but it's not because they aren't sick.

Others here may have better or more accurate explanations --