Acute sarcoid arthritis: occurrence, seasonal onset, clinical features and outcome.

In a 2-yr prospective follow-up study of patients presenting clinically with possible reactive arthritis (ReA), 17 (9%) of the patients turned out to have acute sarcoid arthritis (SA). The number of new cases of SA per year was 2.9/100,000 persons in the city of Oslo between 18 and 60 yr of age. The onset of SA clustered in the spring. All the SA patients presented with bilateral ankle joint involvement and bilateral hilar lymphadenopathy, and ten (59%) presented with the triad of erythema nodosum, arthritis and lung involvement. A prospective follow-up after 104 weeks showed complete remission of arthritis in all 17 cases of SA. The total duration of arthritis [median (range)] was 11 (2-107) weeks. Erythema nodosum was mild and transient in all cases. At week 104, the lung and hilar manifestations had resolved. We conclude that the outcome of SA appeared favourable. Bilateral ankle joint involvement, erythema nodosum and bilateral hilar lymphadenopathy found at the routine chest X-ray examination are important clues for the diagnosis of SA.