Rieger syndrome

Overview

A rare genetic disorder characterized by underdeveloped or absent teeth and craniofacial and eye abnormalities.

Specialists recognize two genetic forms of Rieger syndrome. Type I occurs as a result of mutations on chromosome 4 and Type II results from mutations on chromosome 13.

Symptoms

The main symptoms of Rieger syndrome are: eye anomalies including an underdeveloped iris, a small cornea (microcornea), an opaque ring around the outer edge of the cornea, adhesions in the front of the eye, and displacement of the pupil of the eye so that it is not centered; dental abnormalities including a congenital condition in which fewer teeth than normal (hypodontia) are present, a tooth or teeth that are smaller than normal (microdontia); and/or cone-shaped teeth. 

Other characteristics include craniofacial abnormalities resulting in a face that appears to be flattened, with widely spaced eyes, a broad flat bridge of the nose, under-developed bones of the upper jaw (hypoplasia), and/or a protruding lower lip. 

Some patients with Rieger syndrome may also present with an unusually small anal opening (anal stenosis); failure of the skin around the navel to decrease in size after birth, a condition that is sometimes mistaken for an umbilical hernia; and umbilical hernia, or protrusion of intestine through a weakness in the abdominal wall around the navel. 

Glaucoma, or increased pressure within the eyeball, is sometimes present and can lead to blindness if not treated. This disease can result in damage to the optic disk and gradual loss of vision. The defects in the angle of the eye created by the iris and cornea (trabeculum), the vein at the corner of the eye that drains the water in the eye into the bloodstream (schlemm), and the adhesions associated with Rieger syndrome can lead to glaucoma 

Causes

There are two forms of Rieger syndrome each of which is inherited as an autosomal dominant trait. The form known as Rieger syndrome type I is associated with a change (mutation) in a gene known as RIEG1 on chromosome 4 (4q25-q26). The second form, known as Rieger syndrome type II, has been mapped to gene map locus 13q14 and seems to represent a more complex form of the disorder. Patients with Rieger syndrome type II present with, in addition to the usual signs and symptoms, an enlarged head (hydrocephalus), cardiac defects, more hearing defects and kidney abnormalities. 

Diagnosis

The disorder is commonly recognized by the presence of characteristic eye defects. In some cases these are delayed and diagnosis may be deferred until early childhood when the small, conical teeth become apparent.