Caseous, Necrotic Material and Epithelioid Cell Granulomas in Synovial Fluid from a Patient with Tuberculous Infection

Abstract

The gross appearance and cytologic findings in synovial fluid in tuberculous infections are similar to those in other types of chronic synovial effusion. Demonstration of acid-fast bacilli (AFB) is required for a definitive diagnosis of tuberculous effusion; it is reported in only 20% of cases. The presence of frank caseous necrotic material and epithelioid cell granulomas in synovial fluid samples is unusual but strongly indicative of tuberculous infection.A 28-year-old man, on treatment for pulmonary tuberculosis, presented with a history of right ankle swelling, which was clinically interpreted as nonspecific synovitis. The synovial fluid was yellowish, with fluffy, whitish material. Cytologic smears showed abundant, caseous, necrotic material; a few histiocytic aggregates; and occasional epithelioid cell granulomas. Although stain for AFB was negative, considering the clinical presentation, a diagnosis of tuberculous synovitis could be rendered.Caseous, necrotic material and epithelioid granulomas in synovial fluid are highly unusual but, when present, can be considered definitive evidence of tuberculous effusion, particularly in a known case of pulmonary tuberculosis.