Axenfeld syndrome

Axenfeld syndrome
File:Axenfeld syndrome.jpg 1a Microdontia and hypodontia. 1b Slit pupil and iris atrophy right eye. 1c Corectopia with iris atrophy left eye. 1d Posterior embryotoxon right eye. 1e Posterior embryotoxon left eye. 1f Broad peripheral anterior synechiae right eye.
Classification and external resources
Specialty
ICD-9-CM	743.44
DiseasesDB	30800
Patient UK	Axenfeld syndrome

Axenfeld syndrome (also known as Axenfeld-Rieger syndrome or Hagedoom syndrome) is a rare autosomal dominant disorder, which affects the development of the teeth, eyes, and abdominal region.

Eponym

It is named after the German ophthalmologist Theodor Axenfeld who studied anterior segment disorders, especially those such as Rieger Syndrome and the Axenfeld Anomaly.

The term "Rieger syndrome" is sometimes used to indicate an association with glaucoma. Rieger Syndrome is by medical definition determined by the presence of malformations of the teeth, the underdevelopment of the anterior segment of the eye, along with the manifestations caused by the Axenfeld anomaly. In addition to these occurrences, a prominent Schwalbe's line, an opaque ring around the cornea known as posterior embryotoxon, and hypoplasia of the iris can occur. Glaucoma occurs in up to 50% of patients with Axenfeld-Rieger Syndrome. Other defects such as a lower than average height and stature, a stunt in the development of the mid-facial features and mental deficiencies may be observed.

Diagnosis

Although most recognized for its correlation with the onset of glaucoma, the malformation is not limited to the eye, as Axenfeld syndrome when associated with the PITX2 genetic mutation usually presents congenital malformations of the face, teeth, and skeletal system.

The most characteristic feature affecting the eye is a distinct corneal posterior arcuate ring, known as an "embryotoxon". The iris is commonly adherent to the Schwalbe's line (posterior surface of the cornea).

Analysis of genetic samples from affected patients could result in the discovery of one of the three known genetic mutations which cause the syndrome. About 40% of Axenfeld-Rieger sufferers display mutations in one of the genes known as PAX6, PITX2 and FOXC1.

The OMIM classification is as follows:

Type	OMIM	Gene
Type 1	180500	PITX2
Type 2	601499	possibly FOXO1A
Type 3	602482	FOXC1
DeHauwere syndrome	109120	Unknown

Detection of any of these mutations can give patients a clear diagnosis and post and antenatal procedures such as Preimplantation genetic diagnosis, Chorionic villus sampling and Amniocentesis can be offered to patients. From here, it is a decision for the prospective parent to decide whether they wish to use the genetic diagnosis that they have acquired to prevent the condition from being passed on to future generations.

Pathophysiology

Axenfeld syndrome has an autosomal dominant pattern of inheritance.

The molecular genetics of Axenfeld syndrome are poorly understood, and centers on three genes identified by cloning of chromosomal breakpoints from patients.

This disorder is inheritable as an autosomal dominant trait, which means the defective gene is located on an autosome, and only one copy of the gene is sufficient to cause the disorder when inherited from a parent who has the disorder. As shown in the diagram, this gives a 50/50 chance of offspring inheriting the condition from an affected parent.

See also

• Primary juvenile glaucoma
• SHORT syndrome
• Autosome
• Chorionic villus sampling
• Amniocentesis
• Preimplantation genetic diagnosis

External links

• Axenfeld Rieger syndrome at NIH's Office of Rare Diseases
• Axenfeld Rieger anomaly with cardiac defects and sensorineural hearing loss at NIH's Office of Rare Diseases