Serologic evaluation of patients from Missouri with erythema migrans-like skin lesions with the C6 Lyme test.

Southern tick-associated rash illness (STARI), also known as Masters disease, affects people predominantly in the Southeast and South Central United States. These patients exhibit skin lesions that resemble erythema migrans (EM), the characteristic skin lesion in early Lyme disease. The etiology of STARI remains unknown, and no serologic test is available to aid in its diagnosis. The C6 Lyme enzyme-linked immunosorbent assay was used to evaluate coded serum specimens from patients with STARI at two laboratory sites. The specimens tested at one site consisted of acute- and convalescent-phase samples that were obtained from nine STARI patients from Missouri and from one patient with documented Borrelia lonestari infection who acquired this infection in either North Carolina or Maryland. All of these samples were C6 negative. Seventy acute- or convalescent-phase specimens from 63 STARI patients from Missouri were C6 tested at the second site. All but one of these STARI specimens were also negative. In contrast, of nine acute- and nine convalescent-phase serum specimens obtained from culture-confirmed Lyme disease patients with EM from New York state, seven were C6 positive at the acute stage, and eight were positive at convalescence. The C6 test is negative in patients with STARI, providing further evidence that B. burgdorferi is not the etiologic agent of this disease.