posterior lenticonus

Cataracts, Congenital, Autosomal Recessive 4

Clinical Characteristics
Ocular Features: 

This type of cataract has been reported in a single consanguineous family in which 4 sibs (2 males and 2 females) were diagnosed with cataracts shortly after birth.  Open angle glaucoma developed in two individuals at the age of 7 and 8 years.  The lens opacification involves primarily the posterior subcapsular area.  No genital abnormalities were found in this family.

Another unrelated individual developed progressive cataracts from the age of 2 years.  At cataract surgery it was noted that the posterior capsules were abnormal with thinning of one and a frank lenticonus in the other.

Systemic Features: 

Hypospadias was present in an unrelated male with an inversion of chromosome 9 involving at least two genes.

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the TDRD7 gene (9p22.33).  Normal function of the gene in vertebrates is required for posttranscriptional control of mRNAs critical to normal lens development.

The single unrelated individual with cataracts and hypospadias had an inversion (inv(9)(q22.33q34.11). One of the two breakpoints (9q34.11) involved the gene NR5A1 which is essential for sexual differentiation.  The ocular and genital phenotypes therefore are likely independent. 

The Tdrd7 gene is expressed in lens fibers and its malfunction causes cataracts in mice.  The evolution of lens opacification in mice closely resembles that observed in the reported patient with cataracts and hypospadias.  Some mutant mice develop open angle glaucoma complete with optic atrophy and nerve cupping.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cataract surgery may be indicated and patients should be monitored and treated for glaucoma.

References
Article Title: 

Mutations in the RNA granule component TDRD7 cause cataract and glaucoma

Lachke SA, Alkuraya FS, Kneeland SC, Ohn T, Aboukhalil A, Howell GR, Saadi I, Cavallesco R, Yue Y, Tsai AC, Nair KS, Cosma MI, Smith RS, Hodges E, Alfadhli SM, Al-Hajeri A, Shamseldin HE, Behbehani A, Hannon GJ, Bulyk ML, Drack AV, Anderson PJ, John SW, Maas RL. Mutations in the RNA granule component TDRD7 cause cataract and glaucoma. Science. 2011 Mar 25;331(6024):1571-6.

PubMed ID: 
21436445
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