Abstract
Purpose:
To genetically and phenotypically describe a new ADAM9 mutation in a consanguineous family from Egypt with autosomal recessive cone-rod dystrophy (arCRD) and cataract. To our knowledge, only six families have been described to have arCRD caused by a mutation in ADAM9 and concomitant posterior subcapsular cataract was reported in only one of them.
Methods:
All members of the family were included, the parents and their six children. They underwent a complete ophthalmologic examination including fundus photography and optical coherence tomography (OCT). DNA was extracted from peripheral blood from all family members. An IROme analysis was performed using 64 known genes linked to LCA and one candidate gene, and then high throughput sequencing using Roche Junior was done. To validate our findings, we performed a direct bi-directional sequencing by Sanger sequencing.
Results:
arCRD was diagnosed in the mother and in two children. In addition, bilateral anterior polar and subcapsular cataract was observed in the mother, in the arCRD unaffected children, bilateral dot cataract was diagnosed in two of them, and both bilateral cataract and glaucoma in one. The characteristics the arCRD were childhood-onset visual impairment and a reshuffle of the fundus with white dot deposits, attenuated retinal vessels and mild disc pallor. A coloboma-like macular lesion, with paramacular atrophy and yellow deposits was observed in one of the affected arCRD children. IROme analysis identified a mutation in the splice junction of exon 14 of the ADAM9 gene, c.1396-2A>G, homozygous in the two children affected by arCRD and in the mother, heterozygous in the father and the four unaffected children. The mutation affects the splice junction of exon 14.
Conclusions:
We found a novel autosomal recessive ADAM9 mutation causing arCRD in an Egyptian family with an atypical phenotype. The percentage of arCRD cases caused by mutation in ADAM9 needs to be determined. Since very few families are reported in the literature, the extensive clinical description of ADAM9 families are of significant importance.