At recruitment we presented a case of a 70 year old female with progressive behavioral changes at first concerning for delirium found to have hyponatremia due to HCTZ, decreased food intake and increased fluid intake. However she did not improve after correction of her sodium and continued to have progressive cognitive decline concerning for a rapidly progressive dementia found to be Lyme neuroborreliosis. An important point to bring up regarding testing: IgM serologies are positive during active infection and even though they can remain positive months after initial infection if the titer increases it indicates recurrent active replication. For neuroborreliosis you need both positive serology AND positive CSF anti-Bb antibodies. PCR is available however the “load” that you will see is not indicative of active disease as it will pick up dead spirochetes as well. Additionally PCR can cross react with skin proteins and so can get false positive. It is available as a helpful test is there is diagnostic uncertainty.