What are the test results of rocky mountain spotted fever?

Question

Hi doctor,

I tested positive for rocky mountain spotted fever. I did have two tick bites recently prior to testing. My IgG levels were negative, but my IgM levels came back positive at 1.32. I took 14 days of Doxycycline. My PCP did more blood work due to the fact that I have not been feeling well. I received my results today. My new results show an IgM positive at 1.20, but my IgG levels are still negative. They have prescribed me two more weeks of Doxycycline. Why would I not have anything showing on the IgG part after so long? Is it possible that the IgM levels are showing positive for another reason?

Answer 1

Hi,

Welcome to icliniq.com.

I understand your concerns. I have interpreted the data you provided, and here is my comment:

The diagnosis of RMSF (rocky mountain spotted fever) requires clinical signs and symptoms of skin rash, fever, and muscle pain with positive serology (IgM more than 1/64 and IgG more than 1/64) and positive skin biopsy. As you do not have the rash (on hands and feet), IgG is repeatedly negative, IgM is below 1/64, and you do not have a positive biopsy, I suggest that you do not have RMSF (rocky mountain spotted fever) and another diagnosis should be looked for. If you got bites from ticks, that does not mean that you will be infected with RMSF (rocky mountain spotted fever). Also, you should know that there is cross-reactivity between different types of rickettsia species that explains the weak positive IgM you have. Have you experienced skin rash on your hands and feet? If you have a skin biopsy report, please send it to me.

For further advice, please do not hesitate to follow up.

Wish you all well-being.