Autosomal dominant inheritance of a negative electroretinogram phenotype in three generations.
OBJECTIVE
We report an abnormal electroretinogram with a negative configuration in a child who presented with moderate myopia, nystagmus, and visual developmental delay. We investigated the electroretinogram and explored the possibility of a metabotropic glutamate receptor subtype 6 mutation in six family members spanning four generations.


METHODS
Case report and family study: Complete eye examinations and Ganzfeld electroretinograms were recorded from the maternal great-grandmother, maternal grandmother, mother, uncle, and sibling of the 7-month-old female proband. The electroretinogram was repeated in the proband at 17 months of age. Dark adaptometry was performed in all adult subjects. Fundus photographs and visual field examinations were administered to the grandmother and mother. The metabotropic glutamate receptor subtype 6 gene was amplified and sequenced in all affected subjects.


RESULTS
The proband had a negative electroretinogram and a normal fundus. The maternal grandmother, uncle, and mother had an abnormal electroretinogram identical to the proband yet had no visual complaints. The ophthalmology examinations in the adult subjects were normal, and subsequent examination of the proband at 17 months, 5 years, and 6.5 years of age showed no changes in the fundus or refractive error. Her nystagmus resolved by 5 years of age. Rod threshold and visual fields were normal in the affected adult subjects. No mutation in the metabotropic glutamate receptor subtype 6 gene was found.


CONCLUSIONS
In this family, a negative electroretinogram was not associated with decreased rod threshold, visual acuity loss, visual field loss, muscle disease, or metabotropic glutamate receptor subtype 6 mutation. Additional study will be required to understand the nature of the negative electroretinogram phenotype in this family.
Fitzgerald
K M
KM
Vision Science Laboratory, The Children's Mercy Hospital, University of Missouri-Kansas City School of Medicine, Kansas City, Missouri 64108-9898, USA. kfitzgeral@cmh.edu
Hashimoto
T
T
Hug
T E
TE
Cibis
G W
GW
Harris
D J
DJ
D000328:Adult; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D005799:Genes, Dominant; D006801:Humans; D007223:Infant; D007395:Interneurons / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000150:complications; D009433:Neural Inhibition / Q000235:genetics* / Q000502:physiology; D009759:Nystagmus, Pathologic / Q000150:complications; D010375:Pedigree; D010641:Phenotype; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics; D012160:Retina / Q000502:physiology; D009435:Synaptic Transmission / Q000235:genetics* / Q000502:physiology; D014786:Vision Disorders / Q000150:complications; D014794:Visual Fields
D017931:DNA Primers; D018094:Receptors, Metabotropic Glutamate; C113897:metabotropic glutamate receptor 6