Chromosome 19q cone-rod retinal dystrophy. Ocular phenotype
K. Evans, J. Duvall-Young, F. W. Fitzke, G. B. Arden, S. S. Bhattacharya and A. C. Bird
Department of Clinical Ophthalmology, Institute of Ophthalmology, London.
OBJECTIVE: To describe the phenotype in a family with dominantly inherited
cone-rod dystrophy with chromosome assignment to a 19q locus, and to
correlate this with current classifications of this retinal dystrophy.
DESIGN: A detailed clinical examination including Goldmann perimetry was
undertaken in all family members. Six members under the age of 30 years
underwent dark-adapted electroretinography, color contrast-sensitivity
measurement, dark-adapted static perimetry, and dark adaptometry. PATIENTS:
The study included 34 affected and 22 unaffected patients in four
generations of a pedigree that manifested autosomal dominant cone-rod
retinal dystrophy linked to a chromosome 19q locus by genetic linkage
analysis. RESULTS: Loss of visual acuity occurred in the first decade of
life, onset of night blindness occurred after 20 years of age, and little
visual function remained after the age of 50 years. Central and, later,
peripheral retinal fundus changes were associated with central scotoma,
pseudoaltitudinal field defects, and finally global loss of function.
Psychophysical and electrophysiologic testing before the age of 26 years
showed more marked loss of cone than rod function. CONCLUSIONS: The
phenotype associated with this mutation does not fit well into previous
subtypes of cone-rod dystrophy. Further studies will be needed to correlate
specific genetic mutations in this group of conditions with the various
clinical phenotypes.
