Lyme Borreliosis Incognito-Expanding the Spectrum of Invisible Dermatoses.

We present a 55-year-old patient with rheumatoid arthritis, concomitant small vessel vasculitis, and autoimmune inflammatory myositis who developed a multilocular annular erythema under immunosuppressive therapy. Clinically highly suspicious for Lyme borreliosis, histologically only a minimal perivascular and interstitial dermatitis with discrete mucin deposits was found. Infectious pathogenesis was proven by the detection of borrelia DNA using PCR. This case extends the spectrum of histologically invisible dermatoses and illustrates that in immunocompromised patients, clinically prototypical Lyme borreliosis may only show extremely subtle microscopic features.