Homozygous p.G61E mutation in a consanguineous Pakistani family with co-existence of juvenile-onset open angle glaucoma and primary congenital glaucoma.

Glaucoma is one of the primary causes of visual impairment and blindness in the world. It is characterized by the damage to the optic nerve head and visual field loss. Variants in CYP1B1 are the most common cause of glaucoma in different world populations. We studied a consanguineous Pakistani family in which three affected individuals had a severe form of glaucoma with members in one generation diagnosed with juvenile-onset open angle glaucoma at 27 years of age, while the members of the next generation were affected with primary congenital glaucoma with onset at birth. Sequencing of CYP1B1 revealed a homozygous transition variant, c.182G>A, p.G61E which co-segregated with the disease phenotype. This variant has been previously reported to cause both recessively and dominantly inherited PCG and JOAG in different populations. However, this reported for the first time in Pakistani PCG and JOAG patients in a homozygous state. This is also the first ever report of a CYP1B1 variant segregating in a consanguineous family with co-existence of JOAG and PCG in two subsequent generations. This observation of different phenotypes due to an identical mutation suggests that primary congenital glaucoma and juvenile-onset open angle glaucoma can both be caused by homozygosity for the same mutation. It also indicates the reduced penetrance of the variant in those affected due to p.G61E mutation and further implies that modifiers have a role in controlling the time of onset of the disorder.