CCL cataracts are embryonic in origin, developing during the time when gamma-crystallin genes are active.  The gamma E-crystallin gene is a pseudogene and the mutation in its promoter reactivates its activity 10-fold.  It is postulated that overexpression of the gamma-crystallin fragment is responsible for the nuclear opacification.

Mutations in at least 3 genes have been associated with this type of cataract.  In some families the mutations are in the CRYGC [1] gene (2q33-q35), and in others mutations in CRYBB2 [2] (22q11.2-q12.2) seem to be responsible.  It is of interest that one form of congenital cerulean cataract [3], CCA3 (608983 [4]), found in a single family, results in mutations in CRYGD [5] also located at 22q11.2-q12.2.  A five-generation Chinese family has been reported in which mutations in GJA3 [6] (13q12.11) was associated with this type of lens opacity.

Other forms of autosomal dominantly inherited, congenital, progressive lens opacities include congenital cerulean [3] (115660 [7], 601547 [8], 608983 [4], 610202 [9]), Volkmann type [10] (115665 [11]), lamellar [12] (116800 [13]), and congenital posterior polar [14] (116600 [15]) cataracts. Due to clinical heterogeneity, it is not always possible to classify specific families based on the appearance and natural history of the lens opacities alone.