Iridogoniodysgenesis Syndrome

At a glance

Group of disorders characterized by malformations of the iridocorneal angle of the anterior chamber of the eye, resulting in juvenile glaucoma.

Synonyms

Glaucoma Iridogoniodysgenesis; IGDA Syndrome.

Classification

Two types of iridogoniodysgenesis have been described and consist of:

• Iridogoniodysgenesis Type I (Autosomal Dominant Iridogo­niodysgenesis Anomaly): Characterized by iris hypoplasia, goniodysgenesis, and juvenile glaucoma as a result of aberrant migration or terminal induction of the neural crest cells involved in formation of the anterior segment of the eye.

• Iridogoniodysgenesis Type II (Iridogoniodysgenesis Syndrome; Autosomal Dominant Iris Hypoplasia with Early-Onset Glaucoma): Characterized by an autosomal dominant iris hypoplasia associated with early-onset glaucoma caused by maldevelopment of the trabecular meshwork and the iris. Glaucoma usually is detected in the second decade of life but may begin at any age.

Genetic inheritance

Most cases are transmitted as an autosomal dominant trait with variable expressivity and complete penetrance. Two chromosomal loci can be involved: 4q25 and 6p25, corresponding to PITX2 (or RIEG) and FKHL7, respectively. PITX2, the most studied gene, is a homeobox gene coding for a transcription factor. Different levels of expression of this gene supposedly are responsible for the phenotypic variability of the syndrome.

Pathophysiology

Abnormal differentiation of neural crest cells causes “goniodysgenesis” (abnormalities in differentiation of the iridocorneal angle tissue). The anterior iris stroma is hypoplastic and associated with increased intraocular pressure, resulting in glaucoma.

Clinical aspects

Affected individuals often have an unusual dark-gray or chocolate-brown eye color as a result of the iris epithelium showing through the hypoplastic iris stroma. All patients are at risk for developing juvenile glaucoma, which is often diagnosed in the second decade of life, although it can begin at any age. The glaucoma is often resistant to medical therapy and, in the absence of surgical intervention, blindness may occur. Nonocular features, such as maxillary hypoplasia, dental anomalies (microdontia, hypodontia), umbilical hernia, and hypospadias, may present as part of the syndrome.

Precautions before anesthesia

Inquire about severity of glaucoma and associated nonocular features. Obtain a list of topical antiglaucoma medications: echothiophate (long-acting anticholinesterase, which prolongs the effects of drugs that are metabolized by plasma cholinesterase such as succinylcholine, mivacurium, procaine, chloroprocaine, and cocaine), epinephrine (hypertension and dysrhythmias), and timolol (nonselective beta-blocker with potential for bradycardia, hypotension, bronchospasm in asthmatic patients, and decompensation of congestive heart failure). Selective beta-blockers such as betaxolol are considered safer in asthmatics.

Anesthetic considerations

The main anesthetic challenge is avoidance of intraocular pressure increases during direct laryngoscopy and tracheal intubation, as well as coughing, straining, and vomiting. In the presence of maxillary hypoplasia, intubation per se should not be technically difficult because the mandible ...