Juvenile X-linked retinoschisis from XLRS1 Arg213Trp mutation with preservation of the electroretinogram scotopic b-wave.
OBJECTIVE
To present an Arg213Trp missense mutation in the XLRS1 gene in a family with juvenile X-linked retinoschisis in which one affected male had a normal electroretinogram scotopic b-wave amplitude.


METHODS
Two affected males and one unaffected male from this family with X-linked retinoschisis underwent standard clinical examination including an electroretinogram. Mutations in the XLRS1 gene were detected by sequence analysis and by restriction enzyme assay for loss of an MSP-I restriction site.


RESULTS
A missense mutation of C to T at nucleotide position 637 was identified in exon 6 of the XLRS1 gene. This changed the positively charged arginine to a nonpolar tryptophan (Arg213Trp) within the biologically important discoidin domain. Clinical examination revealed intraretinal cysts in a spoke-wheel distribution and early macular atrophy of the retinal pigment epithelium. Whereas the older affected patient had an "electronegative" electroretinogram typical of retinoschisis, the 13-year-old grandson with the same XLRS1 mutation had a normal electroretinogram scotopic b-wave.


CONCLUSIONS
Although the electroretinogram is a key diagnostic test for X-linked retinoschisis, this report of a normal electroretinogram scotopic b-wave in a male with molecularly confirmed X-linked retinoschisis indicates that caution is advised in relying on the electroretinogram in differential diagnosis of this condition.
Sieving
P A
PA
Department of Ophthalmology, University of Michigan, Ann Arbor, USA.
Bingham
E L
EL
Kemp
J
J
Richards
J
J
Hiriyanna
K
K
D000293:Adolescent; D000328:Adult; D001120:Arginine / Q000235:genetics; D004247:DNA / Q000032:analysis; D003937:Diagnosis, Differential; D004596:Electroretinography; D005091:Exons; D015785:Eye Diseases, Hereditary / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D005136:Eye Proteins / Q000235:genetics*; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D010375:Pedigree; D016133:Polymerase Chain Reaction; D012160:Retina / Q000502:physiology*; D012162:Retinal Degeneration / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D014364:Tryptophan / Q000235:genetics; D014960:X Chromosome / Q000235:genetics*
D005136:Eye Proteins; C108726:RS1 protein, human; D014364:Tryptophan; D004247:DNA; D001120:Arginine