Iris ectopic thyroid tissue: report of a case.

sertion, and dysgenesis of the iridocorneal angle often leading to glaucoma. Although the exact etiology is unknown, CIE arises from late developmental arrest of the posterior migration of neural crest cells. Likewise, abnormal migration and differentiation of cells derived from the neural crest are implied in IND, a disease of the submucous enteric plexus characterized histologically by a large proportion of giant ganglia. In contrast, classic Hirschsprung disease is characterized by the absence of ganglia of the myenteric plexus and submucous plexus in the rectosigmoid. At the molecular level, different factors that may be involved in the development and migration of neural crest cells have been described. The transcription factor Hox11L.1 is thought to be involved in peripheral nervous system development and is expressed by enteric neurons. In addition, genes encoding endothelin 3 or its receptor influence the migration of neuronal crest–derived progenitors. An overexpression of Hox 4 has been found to lead to a misdirection of migratory neuronal progenitors. The association of Hirschsprung disease and iris defects including heterochromia and coloboma is known. However, to our knowledge, the combination of CIE, iridotrabecular dysgenesis, and glaucoma with IND has not been previously described. The combination of both disorders, CIE and IND, underscores their pathogenesis as disorders of neural crest cell migration and differentiation. A genetic defect and the molecular pathogenesis, however, remain to be elucidated.