Rickettsial spotted fever presenting as annular exanthema

A case of rickettsial spotted fever in a 29 year-old woman, zoologist, presenting as annular exanthema is reported. The patient was referred to our clinic on June 1994 because of extensive centripedal erythematous macular rash, clearly annular in appearance, developed 7 days after the onset of high fever (38-39°C), tender enlarged lympho nodes, malaise and headache. Radiological and laboratory investigations did not show visceral involvement. Skin biopsy was refused. The presence of malaise, fever, cutaneous rash, the season, the particular work of the patient, a zoologist, suggested an infectious etiology. Specific serological tests for rickettsial disease were clearly positive for both IgG and IgM anti-Rickettsia conorii, and nonspecific serological test (Weil-Felix reaction) measuring agglutinins to selected antigen from Proteus vulgaris strain OX-l9 was also positive (1:200). After the diagnosis of rickettsial spotted fever, the patient was given oral ambramycin, 1500 mg, daily. Within a few days she was afebrile and symptomatically improved. We underline the rarity of the cutaneous clinical picture featuring as an annular exanthema. To our knowledge, it seems the first report that recognizes a new infectious etiology in the differential diagnosis of occasional annular dermatoses.