**6. Primary congenital glaucoma (PCG)**

In children, PCG is an important cause of visual loss and diagnosed during the neonatal peri‐ od. It is a heterogeneous group of disorder and is characterized by an elevated IOP due to an abnormal development of the aqueous outflow system. The majority of PCG cases are spora‐ dic but there are some familial cases. The familial condition is inherited as an autosomal reces‐ sive trait with variable expression and penetrance. Recently three PCG loci (2p21, 1p36 and 14q24.3-q31.3) corresponding to GLC3A, GLC3B and GLC 3C genes respectively, have been mapped. More than 60 different mutations in CYP1B1 (or GLC3A) – a member of the cyto‐ chrome P450 superfamily enzyme-encoding gene - have been reported in several PCG fami‐ lies [33-38]. Mutations in CYP1B1 were associated with wide range of phenotypes and the alterations of this gene could impair the morphogenesis of the outflow angle because it has been suggested that CYP1B1 gene participates in iridocorneal angle development [39]. In short, the current concept of glaucoma pathogenesis (Fig. 1) suggests that it is a group of het‐ erogeneous optic neuropathies caused by genetic, epigenetic and environmental factor [40].

**Figure 1.** A complex glaucoma pathogenesis may include interplay among several factors such as genetic, epigenetic and environmental factors.
