[Bilobar Thyroid Agenesis]. / Agénésie bilobaire de la thyroïde.

A case of a 27-year-old female patient presenting with bilateral agenesis of the thyroid gland and a benign euthyroid adenoma of the isthmus and the pyramidal lobe is reported. The patient had for several years been followed for a cystic nodule that was presumed to have developed from the left thyroid lobe, having recently increased in size. Scintigraphic and echographic studies evoked the absence of right lobe. Direct examination at cervicotomy found hypoplasia of the two lobes. This report highlights the similarity of this rare anomaly to widely known hemiagenesis.