Primary congenital glaucoma (PCG) is a rare condition (incidence of 1:10,0000), caused by maldevelopment of the trabecular meshwork (trabeculodysgenesis) and anterior chamber angle, resulting in impaired aqueous outflow and raised intraocular pressure (IOP), without other ocular or systemic developmental anomalies.
There are three types:
Cases are usually sporadic, however approximately 10% of cases are autosomal recessive with a variable penetrance. The main gene culprit has been implicated is the CYP1B1 gene. This gene codes for an enzyme that metabolises vital components for ocular development, and Teixeira et al found that in mouse models severe trabecular meshwork atrophy is seen in subjects with a gene deletion.
The MYOC gene on chromosome 1q24 may also explain some cases of PCG, although it is classically associated with primary open angle glaucoma.
Prognosis depends on severity and the age at onset, in true congenital glaucoma, legal blindness happens in at least 50% of eyes.
Primary congenital glaucoma is the most common form, and one of two primary childhood glaucomas presenting in children under four (the other being juvenile open angle glaucoma). If another disease process is present, we can rule out PCG, and other diagnosis need to be considered (e.g. Axenfeld Reiger syndrome, aniridia, Peters anomaly, persistent fetal vasculature, Sturge Weber syndrome, Lowe syndrome, retinopathy of prematurity, tumours and many others).
<aside> ❗ The 2013 International Classification System for Childhood Glaucoma defines childhood glaucoma as irreversible or reversible damage to the whole eye (not just the optic nerve as glaucoma is defined for adults). Therefore, the following clinical signs affecting the whole eye are important to make a diagnosis.
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