i antigen

Cataracts 13, Congenital, in Adult i RBC Phenotype

Clinical Characteristics
Ocular Features: 

The only ocular signs are dense nuclear cataracts with vision in the range of count fingers or light perception.  The opacities are usuallyrecognized at birth.  Some patients develop nystagmus. 

Systemic Features: 

The Ii blood group is associated with cataracts, most strongly in Asians.  The RBC antigens are developmentally regulated.  Fetal and neonatal RBCs express the i form of the antigen which is gradually converted enzymatically to the I form that normally persists in adults.  The normal Ii adult phenotype is reached before the age of two years. 


Homozygous or compound heterozygous deletions of the GCNT2 gene (6p24.3) produce the adult i phenotype (110800) which may or may not be associated with lens opacities.

The GCNT2 gene codes for 3 variants of its product. Mutations that eliminate all 3 GCNT2 variants result in the adult i phenotype in association with congenital cataracts.

Autosomal recessive
Treatment Options: 

Surgery to remove the cataracts may be indicated in some individuals.

Article Title: 

Deletion at the GCNT2 Locus Causes Autosomal Recessive Congenital Cataracts

Irum B, Khan SY, Ali M, Daud M, Kabir F, Rauf B, Fatima F, Iqbal H, Khan AO, Al Obaisi S, Naeem MA, Nasir IA, Khan SN, Husnain T, Riazuddin S, Akram J, Eghrari AO, Riazuddin SA. Deletion at the GCNT2 Locus Causes Autosomal Recessive Congenital Cataracts. PLoS One. 2016 Dec 9;11(12):e0167562.

PubMed ID: 
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