Axenfeld–Rieger syndrome
| Axenfeld–Rieger syndrome | |
|---|---|
| Other names | Axenfeld syndrome, Hagedoom syndrome |
| a) Microdontia and hypodontia. b) Slit pupil and iris atrophy right eye. c) Corectopia with iris atrophy left eye. d) Posterior embryotoxon right eye. e) Posterior embryotoxon left eye. f) Broad peripheral anterior synechiae right eye. | |
| Specialty | Medical genetics |
Axenfeld–Rieger syndrome is a rare autosomal dominant disorder, which affects the development of the teeth, eyes, and abdominal region. It has an estimated prevalence of 1 per 200000 people, without gender predilection, and the inheritance has complete penetrance with variable expressivity. The genes that have been identified in approximately 50% of cases are PITX2 and FOXC1.
Axenfeld–Rieger syndrome is part of the so-called iridocorneal or anterior segment dysgenesis syndromes, which were formerly known as anterior segment cleavage syndromes, anterior chamber segmentation syndromes or mesodermal dysgenesis. Although the exact classification of this set of signs and symptoms is somewhat confusing in current scientific literature, most authors agree with the classification cited here. Axenfeld Anomaly is known as the development of a posterior embryotoxon, associated with strands of the iris adhered to a Schwalbe line that has been displaced anteriorly, which when added to glaucoma is called Axenfeld syndrome. Rieger's anomaly is defined by a universe of congenital anomalies of the iris, such as iris hypoplasia, corectopia or polycoria. When systemic findings are added to Rieger's anomaly, such as bone, facial and/or dental defects, it is known as Rieger syndrome. The combination of both entities gives rise to the Axenfeld–Rieger anomaly when there are no systemic abnormalities and Axenfeld–Rieger syndrome when there are.
To explain the ocular alterations, there is a theory of the mechanism postulated by Shields et al., which implies an arrest in the migration of neural crest cells towards the third trimester of gestation, which leads to the persistence of primordial endothelial tissue in the iris and anterior chamber angle. Contraction of these membranes after birth leads to the progressive changes seen in some patients. This primordial endothelium also generates an excessive and atypical basement membrane, especially near the limbal corneal junction, which accounts for the prominent Schwalbe line. In the case of secondary glaucoma, it would be the consequence of dysgenesis in the chamber sinus.