Ocular coloboma and radial aplasia: syndrome or association

Radial aplasia in CHARGE syndrome: a new association

CHARGE syndrome affects up to 1 in 8500 births, and is most commonly due to de novo truncating mutations in the CHD7 gene. In addition to the 4 major (choanal atresia, coloboma, cranial nerve dysfunction and characteristic ear abnormalities) and 7 minor features (genital hypoplasia, developmental delay, cardiac anomalies, growth retardation, orofacial clefting, tracheo-oesophageal fistula and characteristic facies) proposed by Blake et al. [K.D. Blake, S.L.H. Davenport, B.D. Hall, M.A. Hefner, R.A. Pagon, M.S. Williams, A.E. Lin, J.M. Graham Jr., CHARGE association: an update and review for the primary pediatrician, Clin. Pediatr. (Phila) 37 (1998) 159-173.], many different features have been described in affected patients. Limb defects do not feature in the original designation of the condition, but occasional reports have noted tibial aplasia and other less severe limb anomalies. Presented here is the first case of radial aplasia in a patient with CHARGE syndrome due to a novel frameshift mutation of CHD7.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.