Aniridia-Cerebellar Ataxia-Intellectual Disability Syndrome

A rare, congenital, neurological disorder characterized by the association of partial bilateral aniridia with non-progressive cerebellar ataxia, and intellectual disability.

Epidemiology

To date, less than 30 patients have been reported in the literature.

Clinical description

Aniridia is visible at birth as fixed dilated pupils and is associated with photobia. It can be accompanied with additional ocular findings such as foveal, patchy iris and/or optic nerve hypoplasia, retinal hypopigmentation, and/or pigmentary macular changes leading to reduced visual acuity. Cataract and corneal opacities are never observed. Non-progressive cerebellar ataxia is associated with delayed developmental milestones and hypotonia (visible from the first year of life), gait and balance disorders with incoordination, intention tremor, and scanning speech. Intellectual disability is variable. Mild facial dysmorphic features may be observed such as high forehead, hypertelorism, epicanthic folds, depressed nasal bridge with anteverted nostrils, and thin upper lip. The cases referred to as atypical Gillespie syndrome correspond to those showing a more complex phenotype, associating additional ocular findings and a mild dysmorphic face.

Etiology

The etiology is unknown. Some atypical cases have been linked to mutations in the PAX6 gene (11p13), encoding a transcriptional regulator expressed in ocular, cerebral, olfactory, and pancreatic tissues. One case has also been reported to be due to a de novo translocation of chromosome X and 11 t(X;11) (p22.32;p12), but with no involvement of the PAX6 gene.

Diagnostic methods

A presumptive diagnosis can be made in the first months of life: on slit lamp examination, the pupil border of the iris typically shows a scalloped, 'festooned' edge with iris strands extending onto the anterior lens surface at regular intervals. In many cases, neuroimaging studies (CT scan, MRI) show cerebellar hypoplasia or atrophy, especially of the vermis, with occasional white matter changes, and diffuse atrophy of the cerebral hemispheres, brainstem and frontal cortex.

Differential diagnosis

Differential diagnosis includes Marinesco-Sjögren syndrome (see this term) in which congenital cataract is present, as well as cerebellar ataxia, intellectual disability, and aniridia (see this term).

Genetic counseling

Sporadic and familial cases have been observed. Although some reported families are compatible with autosomal dominant inheritance, Gillespie syndrome is more likely to be an autosomal recessive condition.

Management and treatment

Management includes regular ophthalmologic evaluation with prescription of optical aids, physical, speech and occupational therapy for muscular re-education.

Prognosis

There are no reports on the natural history of the disease. Prognosis depends on the proper management and anticipation of ocular and mental symptoms and disabilities.