An elderly immunocompromised woman who developed meningoencephalitis was most likely infected with Borrelia miyamotoi, which is related to the spirochete that causes Lyme disease and may be an underappreciated cause of disease in locations where Lyme disease is endemic.

Real-time PCR testing of cerebrospinal fluid samples confirmed the presence of the Borrelia species in this patient, but ruled out the presence of the Lyme disease pathogen B. burgdorferi, according to Sam R. Telford III, ScD, of Tufts University in North Grafton, Mass., and colleagues.

Instead, amplification of two genes specific to B. miyamotoi implicated this organism, a finding that "was confirmed by sequencing and phylogenetic analysis of the 16S rRNA and flagellin genes," and "that definitively place the Borrelia from this patient within the American clade of the B. miyamotoi-like spirochetes," the researchers reported in the Jan. 17 issue of the New England Journal of Medicine.