7q35-q36 locus

Glaucoma, Pigment Dispersion Syndrome

Clinical Characteristics
Ocular Features: 

This is a form of open angle glaucoma with early onset (usually before the age of 40 years).  Marked pigment deposition in the trabecular meshwork, on the lens, zonules, and the corneal endothelium can often be seen prior to elevation of the intraocular pressure. It can be present asymmetrically, even unilaterally, but primarily in early stages.  The pigment source in humans seems to be the iris in which hypopigmentation leads to radial transillumination defects and mouse models corroborate this.  The iris configuration is sometimes described as flat or even concave.  The pattern of pigment deposition on the posterior surface of the cornea is known as a Krukenberg spindle and considered diagnostic.  Untreated, the characteristic optic nerve damage and visual field changes of glaucoma eventually occur.  Early-onset and rapidly progressive nuclear cataracts have been reported in some patients.

In one longitudinal study of 113 patients diagnosed with pigment dispersion and followed for 24 years, 23 had glaucoma initially and 9 more eventually required treatment for elevated pressure. The mean age at diagnosis was 42 years and myopic males were the most commonly affected.

The syndromic nature of PDS is suggested by the association of lattice degeneration, retinal tears, and detachments in a significant number of individuals.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal dominant form of glaucoma-related optic neuropathy that shares some features with open angle juvenile glaucoma (137750), such as myopia and early onset.  The pigment dispersion syndrome described here, however, maps to a different locus (7q35-q36).  Another candidate locus is located at 18q11-q21 but the causative mutations remain elusive.

A four generation family with an apparent autosomal recessive pattern has been reported.

The autosomal dominant pattern is not always apparent from history alone and examination of relatives is necessary to document the familial nature of this disease. 

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

The usual glaucoma therapies are indicated.  Some have advised limiting vigorous impact sports to reduce the amount of pigment released.  All individuals with pigment dispersion must be followed vigilantly for development of glaucoma as the risk is high.  It has been estimated to be 10% within 5 years and 15% in 15 years, regardless of age and family history.  Further, the pigment dispersion is progressive along with the risk of elevated pressure as eventually 30 -50% of patients develop glaucoma.  However, regression of pigment deposition, decrease of iris transillumination and even stabilization of pressure has also been noted in some, mostly younger, patients.

Laser iridotomy has been suggested as therapeutically useful in the reduction of the IOP but there is no statistical confirmation of this.

References
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