Atypical Rocky Mountain spotted fever with polyarticular arthritis

Rocky Mountain spotted fever (RMSF) is an acute, serious tick borne illness caused by Rickettsia rickettsi. Frequently, RMSF is manifested by headache, a typical rash and fever but atypical disease is common, making diagnosis difficult. Inflammatory arthritis as a manifestation is rare. The purpose of this study is to describe a patient with serologically proven RMSF who presented in an atypical manner with inflammatory arthritis of the small joints of the hands and to review the previously reported patients with rickettsial infection and inflammatory arthritis.

An 18-year-old woman presented with a rash that began on the distal extremities and spread centrally, along with hand pain and swelling. She had tenderness and swelling of the metacarpophlangeal joints on examination in addition to an erythematosus macular rash and occasional fever.

Acute and convalescent serology demonstrated R rickettsi infection. She was successfully treated with doxycycline.

Inflammatory arthritis is a rare manifestation of RMSF or other rickettsial infection with 8 previously reported patients, only 1 of whom had RMSF. Physician must have a high index of suspicion for RMSF because of atypical presentations.