Congenital cataracts are highly heterogeneous disorders at both the genetic and clinical-phenotypic levels. They are one of the major causes of vision loss in children worldwide and are responsible for about one-third of cases of blindness in infants. Cataracts can lead to permanent blindness by interfering with the sharp focus of light on the retina, especially during the early developmental periods. They can be classified clinically according to the part of the opacified lens, including nuclear, cortical, lamellar, sutural, polar, or subcapsular cataract. Nuclear cataracts affect the central nucleus of the eye, are often not highly visually significant. This type of cataract progresses, it changes the eye's ability to focus, and close-up vision may temporarily improve. Pulverulent cataracts are characterized by a dust-like, 'pulverised' appearance of the opacities which can be found in any part of the lens. “Cataract 17, multiple types” includes nuclear and pulverulent cataracts, among others.
Khan et al (2012) conducted a study on 10 consanguineous Saudi families with multiple affected members with central pulverulent cataract. There were 16 children (7 girls and 9 boys) aged between 4-16 years, they all had characteristic multiple central nuclear punctate lenticular opacities bilaterally. Two patients (same family) had cortical riders and six had associated strabismus. Homozygosity mapping for one of the families revealed a candidate gene CRYBB1 within Chr22q21.1 region. Sequence analysis of the CRYBB1 gene was performed in all affected patients; a homozygous c.171del mutation was identified with a shared haplotype in all 16 children.