Axenfeld Anomaly and Syndrome

Definition: Axenfeld anomaly, also called posterior embryotoxon, is a congenital anomaly in which Schwalbe’s line (arrow #1) is anteriorly displaced and associated with iris bands that extend to the cornea (arrow #2). If the development of the meshwork is defective and glaucoma is present, the condition is called Axenfeld syndrome. The Rieger anomaly is the term used to describe iris and pupillary abnormalities in combination with the findings of the Axenfeld anomaly. The Reiger anomaly is associated with the later onset of glaucoma. If the Rieger anomaly is associated with dental and skeletal abnormalities, the condition is called the Rieger syndrome.
History: Axenfeld described this abnomality in 1920.
Incidence/Prevalence: 50% of patients with the Axenfeld anomaly have been reported to progress to develop glaucoma.
Etiology: Mutations of the FOXC1 gene and in the PITX2 gene have been described in families with the Axenfeld-Rieger syndrome (1,2).
Clinical Findings: Axenfeld anomaly manifests as a crescentic shaped opacity in the peripheral cornea. Schwalbe’s line is not visible normally, so the presence of this ring is clinically diagnostic. Strands may extend from the iris periphery to the cornea. If the angle structures are normal and there is no glaucoma this is called the Axenfeld anomaly.
Histopathology: Sections show anterior displacement and usually thickening of Schwalbe's line. Schwalbe's line appears in section as a collagenous nubbin (arrow 3 in Figure). Frequently, iris processes extend from the peripheral iris to insert at Schwalbe's line on the cornea (arrow 4). Notice in the photograph that there is a thin Descemet's membrane and endothelium on either side of Schwalbe's line indicating it is abnormally displaced anteriorly and interposed between clear cornea.
Treatment: Trabeculostomy and trabeculectomy have been performed in patients with Axenfeld syndrome.
References:
1. Panicker SG et al. Invest Ophthalmol Vis Sci. 2002; 243:3613-6.
2. Borges AS et al. J Glaucoma. 2002;11:51-6