Br J Ophthalmol 1999;83:1144-1148
( October )
Difference between RP2 and RP3 phenotypes in X linked retinitis
pigmentosa
Christina J Flaxel* a, Marcelle Jaya, Dawn L Thiseltona, Mani Nayudua, Alison J Hardcastlea, Alan Wrightb, Alan C Birda
a Institute of
Ophthalmology and Moorfields Eye Hospital, London, b MRC Human Genetics
Unit, Western General Hospital, Edinburgh* Currently affiliated with the University of Southern
California, Doheny Eye Institute, Los Angeles, CA, USA.
Correspondence to: Professor Alan Bird, Moorfields Eye Hospital, City Road, London
EC1V 2PD.
Accepted for publication 25 June 1999
AIM
X linked retinitis
pigmentosa (XLRP) has two genetic loci known as "RP2" and
"RP3". Clinical features reported to differentiate RP2 from RP3
include a higher prevalence of myopia and primary cone dysfunction in
RP2, and late onset night blindness and tapetal reflex in RP3. Members
from 14 XLRP families were examined in an attempt to verify these differences.
METHODS16 affected
males and 37 females from 14 XLRP families assigned as either RP2 or
RP3 by haplotype analysis and/or by heterogeneity analysis were
examined. Members of all 14 families who were willing to participate
but unavailable for examination were contacted and detailed interviews
carried out.
RESULTSNo clear
phenotypic differences were found that could be used to reliably
differentiate RP2 from RP3 with respect to myopia and onset of night
blindness. The tapetal reflex was also found to be present in carriers
of both RP2 and RP3.
CONCLUSIONSXLRP is a
heterogeneous class of rod degenerative disorders with no clear
phenotypic differentiation between the two genetic loci RP2 and RP3.
There is a continuum of clinical presentations which can be seen in
both RP2 and RP3, but the features within a given family tend to be
consistent. However, interfamilial variability is prevalent leading to
a wide range of clinical presentations and more than one abnormal
allele at each gene locus cannot be excluded.
© 1999 by British Journal of Ophthalmology
