Prevalence of primary and secondary fibrositis.

Of 1,473 consecutive new patients seen in an outpatient rheumatology clinic, 3.7% met criteria for "primary fibrositis." Secondary fibrositis was diagnosed in 12.2% of patients with rheumatoid arthritis (RA), 15.7% of patients with primary neck and back pain syndromes and 6.7% of patients with osteoarthritis (OA). When conditions presumed to be associated with secondary fibrositis were excluded, primary fibrositis was identified in 55 of 405 patients or 13.6%. Two hundred fifteen or 14.6% of all patients had either primary or secondary fibrositis. Fibrositis may be the most common disorder seen in rheumatic disease practice after OA and RA.