What does slightly-BELOW normal levels of IgG proteins in the CNS (as determined during a LP) indicate?

Question

I was being checked for MS (due to "abnormality" on optic nerve and "multiple spots" on the left parietal lobe found during an MRI). My neuro ordered an LP. Not only did it come back with no o-bands, but my IgG levels were "slightly below normal"--and in potential MS cases, they're generally elevated? My follow up with my neuro isn't for another month, so I wondered--does this rule out MS? Does it point to anything else?

Answer 1

This lumbar puncture finding does not entirely rule out Multiple Sclerosis, but it does suggest against it. 5-15% of people with MS will not have o-bands.

There are no particular diseases characterized by low levels of IgG. Hypogammaglobulinaemias could be what has caused this, but more likely it is in fact a normal variation and just happened to be low at the time of the test.