Suppurative thyroiditis: an unusual case caused by Actinomyces naeslundi.

A case of suppurative thyroiditis due to A.naeslundi is recorded. The clinical features (including the difficulty in establishing a clinical diagnosis) have been noted. This is the first instance of A.naeslundi being considered the etiological agent of actinomycosis of the thyroid. It is also the first report incriminating A.naeslundi as a pathogen, since up to now it was considered only a saprophyte.The etiological role of A.naeslundi in this case of suppurative thyroiditis is strongly supported by the following findings:1. A.naeslundi was isolated without the presence of other pathogenic micro-organisms.2. A sulphur granule was demonstrated in the caseous pus after incision of the abscess.3. There was a favourable response to specific antibiotic therapy.