During embryonic development the thyroid gland migrates through the thyroglossal duct from the pharyngeal endoderm to the anterior cervical region. The final step in this process is the total obliteration of the thyroglossal duct. A case is presented of a patient with a thyroglossal cyst together with a complete failure of the obliteration of the duct, which caused regurgitations of mucopurulent material after the expression of the cyst. This indicates a complete failure of the obliterative process. To the best of our knowledge, this phenomenon has not been described previously in the literature.