Ocular Findings in Patients With Autosomal Dominant Retinitis Pigmentosa and Rhodopsin, Proline-347-Leucine
Eliot L. Berson, M.D., Bernard Rosner, Ph.D., Michael A. Sandberg, Ph.D., Carol Weigel-DiFranco, M.A., and Thaddeus P. Dryja, M . D .
We s t u d i e d t h e o c u l a r findings i n e i g h t u n related patients with a form of a u t o s o m a l dominant retinitis pigmentosa and the same c y t o s i n e - t o - t h y m i n e t r a n s i t i o n in the second nucleotide of codon 347 of the rhodopsin gene. T h i s m u t a t i o n , detected in l e u k o c y t e DNA, corresponds to a substitution of leucine for p r o l i n e in a m i n o a c i d 3 4 7 o f t h e r h o d o p s i n protein, and, therefore, we designated this form of retinitis p i g m e n t o s a as rhodopsin, proline-347-leucíne. On average, these pa t i e n t s h a d s i g n i f i c a n t l y s m a l l e r v i s u a l field areas and smaller electroretinogram ampli t u d e s t h a n 1 4 0 u n r e l a t e d p a t i e n t s of c o m p a r a ble age with dominant retinitis pigmentosa w i t h o u t t h i s m u t a t i o n . T h e findings i n e i g h t relatives with this mutation from three of these families are p r e s e n t e d to p r o v i d e e x a m p l e s of t h e v a r i a b i l i t y t h a t e x i s t s i n t h e c l i n i cal s e v e r i t y o f t h i s d i s e a s e .
A RESTRICTION fragment length polymorphism within the long arm of h u m a n c h r o m o s o m e 3 h a s b e e n l i n k e d to t h e d i s e a s e t r a i t in a l a r g e family in I r e l a n d w i t h a u t o s o m a l d o m i n a n t r e t i nitis pigmentosa.' Since the rhodopsin gene a l s o m a p s to t h e l o n g a r m o f c h r o m o s o m e 3^·^ a n d s i n c e r h o d o p s i n is e x p r e s s e d in r o d p h o t o -
Accepted for publication Feb. 18, 1991. From the Berman-Gund Laboratory for the Study of Retinal Degenerations and the Howe Laboratory of Oph thalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts. This study was supported in part by National Eye Institute grants EY00169 and EY02014 and grants from the Na tional Retinitis Pigmentosa Foundation, Baltimore, Maryland, and the George Gund Foundation, Cleveland, Ohio. Dr. Berson is a Research to Prevent Blindness Senior Scientific Investigator. Reprint requests to Eliot L. Berson, M.D., Massachu setts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114.
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r e c e p t o r s t h a t are a f f e c t e d e a r l y in t h i s d i s ease,^* w e h a v e b e e n s e a r c h i n g for a b n o r m a l i t i e s in t h e r h o d o p s i n g e n e in t h e l e u k o c y t e DNA o f p a t i e n t s w i t h d o m i n a n t r e t i n i t i s p i g mentosa. We p r e v i o u s l y d e s c r i b e d f o u r d i s t i n c t p o i n t m u t a t i o n s in t h e g e n e c o d i n g for r h o d o p s i n . " ' O f 1 4 8 unrelated patients from separate fami l i e s r e s i d i n g in t h e U n i t e d S t a t e s o r C a n a d a with autosomal dominant retinitis pigmentosa, 2 7 c a r r y o n e o f t h e s e four m u t a t i o n s . E a c h mutation corresponds to a single a m i n o acid s u b s t i t u t i o n in t h e r h o d o p s i n p r o t e i n . T h e s e rhodopsin mutations and their frequencies by f a m i l y a r e as f o l l o w s : p r o l i n e - 2 3 - h i s t i d i n e , 1 7 cases ( 1 2 % ) ; proline-347-leucine, eight cases (5%); proline-347-serine, one case ( 0 . 5 % ) ; and threonine-58-arginine, one case ( 0 . 5 % ) . Only o n e m u t a t i o n h a s b e e n f o u n d in a n y g i v e n family, and each mutation h a s segregated per f e c t l y w i t h t h e d i s e a s e trait in t h e f a m i l i e s s t u d i e d . W e h a v e n o t o b s e r v e d t h e s e m u t a t i o n s in 106 unrelated normal individuals. T h e s e results suggest that these mutations are the cause o f some forms o f dominant retinitis pigmentosa."' We s t u d i e d t h e o c u l a r findings i n e i g h t u n r e lated patients with dominant retinitis pigmen tosa and rhodopsin, proline-347-leucine. Their findings are c o m p a r e d with those from 1 4 0 patients without this mutation. We also studied e i g h t r e l a t i v e s from t h r e e o f t h e s e f a m i l i e s to show the range of abnormalities that exists among patients with this mutation.
Patients and Methods We r e v i e w e d t h e c l i n i c a l findings o f 1 4 8 p a tients, ages 1 8 to 4 9 years, with autosomal dominant retinitis pigmentosa who had donat ed a b l o o d s p e c i m e n for m o l e c u l a r g e n e t i c s t u d ies o f t h e i r l e u k o c y t e D N A . A l l 1 4 8 p a t i e n t s
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TABLE 1 FINDINGS ON HISTORY IN AFFECTED PATIENTS CASE NO., FAMILY NO., AGE (YB8), SEX
AGE OF ONSET OF NIGHT BLINDNESS (YB8)
AGE OF ONSET OF DIFFICULTY WITH SIDE VISION (YRS)
1,6003,22, Μ 2, 3570, 25, Μ 3, 0140, 30, Μ 4, 6073, 31, F 5, 5683, 32, F 6, 5864, 35. F 7,0771,35, Μ 8, 6473, 45, Μ
14 12 Near birth 8 13 16 6 18
14 20 12 16 27 22 23 21
w e r e from s e p a r a t e families a n d resided in t h e U n i t e d States o r C a n a d a . E a c h p a t i e n t w a s from a family with a d o m i n a n t m o d e of t r a n s m i s s i o n of retinitis p i g m e n t o s a o v e r at least t h r e e c o n secutive g e n e r a t i o n s . E i g h t of t h e s e p a t i e n t s had a cytosine-to-thymine transition heterozygously in t h e s e c o n d n u c l e o t i d e b a s e of c o d o n 3 4 7 ( c y t o s i n e - c y t o s i n e - g u a n i n e to c y t o s i n e - t h y mine-guanine) corresponding to a substituton of l e u c i n e for p r o l i n e , w h e r e a s 1 4 0 of t h e s e p a t i e n t s did n o t h a v e this m u t a t i o n . ' All 1 4 8 patients had retinal arteriolar narrowing; most h a d i n t r a r e t i n a l b o n e spicule p i g m e n t a t i o n . W e also r e v i e w e d the o c u l a r findings in eight clini
cally affected r e l a t i v e s of t h r e e of t h e eight p a t i e n t s w i t h this m u t a t i o n . T h e s e relatives were selected because they had already provid e d b l o o d s p e c i m e n s for D N A a n a l y s i s ; all e i g h t relatives a l s o h a d t h e s a m e c y t o s i n e - t o - t h y m i n e t r a n s i t i o n in t h e s e c o n d n u c l e o t i d e b a s e of c o d o n 3 4 7 of t h e r h o d o p s i n g e n e . All eight p a t i e n t s w i t h this m u t a t i o n h a d E u r o p e a n family origin w i t h n o single c o u n t r y p r e d o m i n a t i n g . T h r e e r e s i d e in N e w E n g l a n d , t w o in t h e m i d - A t l a n t i c s t a t e s , a n d t h r e e in midwestern states. T h e 1 4 8 p a t i e n t s w i t h d o m i n a n t r e t i n i t i s pig mentosa completed a questionnaire regarding t h e a g e of o n s e t o f n i g h t b l i n d n e s s a n d a g e of o n s e t of difficulty w i t h s i d e o r p e r i p h e r a l vi sion. W e e v a l u a t e d their d i s t a n c e S n e l l e n a n d F e r r i s visual a c u i t i e s , k i n e t i c G o l d m a n n visual fields, i n t r a o c u l a r p r e s s u r e b y a p p l a n a t i o n t o n o m e t r y , d a r k - a d a p t e d full-field e l e c t r o r e t i n o g r a m s , r e t i n a l visual a c u i t i e s , s l i t - l a m p a p p e a r ance of e a c h lens, and fundus a p p e a r a n c e by o p h t h a l m o s c o p y a s d e s c r i b e d p r e v i o u s l y . ' Slitlamp examination was performed to determine p r e s e n c e or a b s e n c e o f a c e n t r a l p o s t e r i o r s u b c a p s u l a r c a t a r a c t in e a c h eye. O p h t h a l m o s c o p i c examination was performed to determine w h e t h e r or n o t c y s t o i d m a c u l a r e d e m a c o u l d be s e e n a n d w h e t h e r i n t r a r e t i n a l b o n e s p i c u l e pig m e n t w a s in the p e r i p h e r y in all f o u r q u a d r a n t s .
TABLE 2 FINDINGS ON OCULAR EXAMINATION IN AFFECTED PATIENTS
VISUAL ACUITY CASE NO., AGE (YRS)
1,22 2, 25 3,30 4, 31 5,32 6,35 7,35 8,45
EYE
SNELLEN
FERRIS*
RETINAL
R.E. L.E. R.E. LE. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E.
20/27 20/30 20/85 20/82 20/20 20/20 20/21 20/21 20/33 20/52 20/37 20/41 20/37 20/30 20/93 20/42
54 47 24 31 59 59 58 58 50 39 44 41 44 47 31 42
20/33 20/37 20/112 20/120 20/20 20/24 20/20 20/20 20/36 20/42 20/37 20/34 20/25 20/25 20/102 20/47
REFRACTIVE ERROR
+0.50 -1.25 X 95 +0.50 -1.75 X 80 +2.00 -1.50 X 172 +3.00 -1.87 X 170 +0.87 -0.87 X 15 +0.87 -1.12 X 160 -1.37 -0.62 X 7 -1.75 -1.00 X 180 +0.87 -2.50 X 15 +0.50 -3.00 X 177 -0.62 -0.50 X 22 +0.37 -3.25 -0.62 X 60 -3.37 -0.50 X 150 + 1.25 -0.75 X 157 +0.75 -1.25 X 177
•Number of letters read; 65 letters equals Snellen equivalent of 20/20.
LENS
Clear Clear Posterior subcapsular opacity Posterior subcapsular opacity Clear Clear Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity
INTRARETINAL BONE SPICULE PIGMENT IN FOUR QUADRANTS
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
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V i s u a l fields w e r e p l o t t e d w i t h a d i g i t i z i n g t a b l e t , a n d the t o t a l a r e a for e a c h e y e w a s q u a n t i f i e d b y a c o m p u t e r in s q u a r e d e g r e e s a n d e x p r e s s e d a s a n e q u i v a l e n t c i r c u l a r a r e a or equivalent circular diameter. Electroretino g r a m s w e r e q u a n t i f i e d w i t h r e s p e c t to p e a k - t o p e a k a m p l i t u d e s for t h e m i x e d c o n e - r o d r e s p o n s e s t o 0 . 5 - H z w h i t e flashes, t h e c o n e - i s o l a t e d r e s p o n s e s to 3 0 - H z w h i t e flashes, a n d t h e 3 0 - H z c o n e b-wave implicit times (that is, the t i m e i n t e r v a l s b e t w e e n e a c h flash o f l i g h t a n d t h e c o r r e s p o n d i n g c o r n e a - p o s i t i v e p e a k ) as d e scribed previously.' T h e data derived from ocular e x a m i n a t i o n s o f the 1 4 8 patients with d o m i n a n t retinitis pig mentosa were coded by one person and checked b y a n o t h e r ; data w e r e t h e n k e y p u n c h e d , v e r i fied, a n d s t o r e d on a m a g n e t i c t a p e for d a t a p r o c e s s i n g . D a t a w e r e t h e n v a l i d a t e d for e r r o r s a n d i n c o n s i s t e n c i e s a n d c o r r e c t e d as n e c e s s a r y . Comparisons were made between the group of eight unrelated patients with this mutation and the group of 1 4 0 unrelated patients without this mutation. Each o f the 1 4 8 patients was e x a m i n e d t w i c e w i t h i n s i x w e e k s , a n d a n aver a g e s c o r e for e a c h e y e w a s c o m p u t e d for e a c h test p a r a m e t e r . F o r t h e p u r p o s e o f s t a t i s t i c a l a n a l y s i s , a n a v e r a g e o f t h e s e s c o r e s for t h e t w o eyes was used. Since the distributions o f S n e l len distance visual acuities, retinal visual acui t i e s , v i s u a l field e q u i v a l e n t c i r c u l a r a r e a s , a n d electroretinogram amplitudes were skewed, the data w e r e t r a n s f o r m e d u s i n g t h e log^ s c a l e to a p p r o x i m a t e b e t t e r a n o r m a l d i s t r i b u t i o n for e a c h p a r a m e t e r for p u r p o s e s o f s t a t i s t i c a l a n a l ysis. D a t a for c o n t i n u o u s v a r i a b l e s , s u c h as best-corrected visual acuity or spheric refrac tive e r r o r , w e r e a n a l y z e d u s i n g f-tests for u n i v a r i a t e a n a l y s e s . ' " D i s c r e t e v a r i a b l e s , s u c h as p r e s e n c e or a b s e n c e o f p o s t e r i o r s u b c a p s u l a r c a t a r a c t in b o t h e y e s or p r e s e n c e or a b s e n c e o f b o n e s p i c u l e p i g m e n t in all f o u r q u a d r a n t s o f t h e f u n d u s p e r i p h e r y in b o t h e y e s , w e r e a n a l y z e d w i t h t h e Y a t e s c o r r e c t e d c h i - s q u a r e test or F i s h e r ' s e x a c t test.'" A g e o f o n s e t o f n i g h t b l i n d n e s s a n d a g e o f o n s e t o f difficulty w i t h s i d e vision were evaluated by using the log-rank life-table m e t h o d o f analysis; patients w h o did n o t yet h a v e n i g h t b l i n d n e s s or w h o h a d n o t yet r e p o r t e d v i s u a l field l o s s w e r e t r e a t e d a s c e n sored observations with the length of the f o l l o w - u p p e r i o d e q u a l to t h e i r c u r r e n t a g e . " Multiple regression analysis used group m e m bership, age, and sex as the independent varia b l e s a n d s e l e c t e d o c u l a r findings a s t h e d e p e n dent variables. This allowed assessment of
TABLE 3 VISUAL FIELDS A N D ELECTRORETINOGRAMS IN A F F E C T E D PATIENTS
ELECTRORETINOGRAM'
VISUAL FIELD* C A S E NO.,
0.5-H2
30-HZ
30-HZ
AMPLI
AMPLI
IMPLICIT
TUDE
TUDE
TIME
A G E (YRS)
EYE
AREA
DIAMETER
(MV)
(MV)
(MSEC)
L22
R.E. L.E. R.E. LE. R.E. L.E. R.E. LE. R.E. LE. R.E. LE. R.E. L.E. R.E. LE.
7194 6742 384 326 2197 2222 2718 3052 2075 1992 186 189 1658 1773 484 536
96 93 22 20 53 53 59 62 51 50 15 15 46 47 25 26
3.3 2.9 1.2 1.7 1.8 3.0 3.2 2.7 1.6 1.6 1.1 NA* 1.0 1.3 1.0 1.0
1.1 1.4 1.0 1.1 1.0 1.2 0.7 0.6 0.2 0.2 0.2 0.2 0.7 0.6 0.3 0.3
47 48 42 43 40 41 39 41 34 34 43 47 35 34 33 34
2,25 3, 30 4, 31 5,32 6,35 7,35 8,45
*Area is ttie visual field area Including periptieral islands in degrees squared to a V«, white test light. Lower limit of normal is 11,399 degrees squared. Diameter is equivalent circular diame ter in degrees: 2 V ^ . •Full-field electroretinograms: normal limits are 0.5-Hz white > 350 MV; 30-Hz white flicker s 50 μΨ, and 30-Hz b-wave implicit time s 32 msec. «NA indicates not available.
differences b e t w e e n the two groups for selected o c u l a r findings after c o r r e c t i n g f o r a g e a n d sex.'" We e x a m i n e d eight affected relatives from three of the families o n c e . Their clinical findings p r o v i d e a d d i t i o n a l d a t a o n t h e r a n g e o f ocular abnormalities seen in patients with this mutation and show examples of some variabili ty o f c l i n i c a l e x p r e s s i o n o f t h i s c o n d i t i o n among patients of comparable age.
Results T h e e i g h t p a t i e n t s from s e p a r a t e f a m i l i e s with dominant retinitis pigmentosa and rhodopsin, p r o l i n e - 3 4 7 - l e u c i n e reported s o m e var i a b i l i t y in t h e a g e o f o n s e t o f n i g h t b l i n d n e s s (Tables 1 through 3 ) . For example, one patient
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TABLE 4 GROUP COMPARISONS OF PATIENTS WITH (GROUP 1) AND WITHOUT (GROUP 2) PROLINE-347-LEUCINE RHODOPSIN MUTATION
PARAMETERS
GROUP 1 (N = 8)
GROUP 2 (N = 140)·
f-STAT
RVALUE
Ρ VALUE (CORRECTED)'
Snellen* visual acuity Ferris visual acuity Retinal* visual acuity Spheric refractive error Cylindric refractive error Intraocular pressure (mm Hg) Visual field area (deg^ 0.5-Hz electroretinogram (/tV)* 30-Hz electroretinogram (/tV)* 30-Hz electroretinogram (msec)
+0.61 ± 0.49 (20/37)
+0.54 ± 0.54 (20/34)
+0.33
NS
NS
-0.92
NS
NS
+45.28 ± 10.48
+48.36 ± 9.16
+0.64 ± 0.59 (20/38)
+0.48 ± 0.40 (20/32)
+1.08
NS
NS
+0.07 -1.19 12.16 7.11 0.52 -0.62 39.44
-0.21 -1.16 11.92 7.99 1.79 +0.65 42.22
+0.21 +0.10 +0.31 -1.84 -6.57 -4.27 -1.73
NS NS NS NS
Eliot L. Berson, M.D., Bernard Rosner, Ph.D., Michael A. Sandberg, Ph.D., Carol Weigel-DiFranco, M.A., and Thaddeus P. Dryja, M . D .
We s t u d i e d t h e o c u l a r findings i n e i g h t u n related patients with a form of a u t o s o m a l dominant retinitis pigmentosa and the same c y t o s i n e - t o - t h y m i n e t r a n s i t i o n in the second nucleotide of codon 347 of the rhodopsin gene. T h i s m u t a t i o n , detected in l e u k o c y t e DNA, corresponds to a substitution of leucine for p r o l i n e in a m i n o a c i d 3 4 7 o f t h e r h o d o p s i n protein, and, therefore, we designated this form of retinitis p i g m e n t o s a as rhodopsin, proline-347-leucíne. On average, these pa t i e n t s h a d s i g n i f i c a n t l y s m a l l e r v i s u a l field areas and smaller electroretinogram ampli t u d e s t h a n 1 4 0 u n r e l a t e d p a t i e n t s of c o m p a r a ble age with dominant retinitis pigmentosa w i t h o u t t h i s m u t a t i o n . T h e findings i n e i g h t relatives with this mutation from three of these families are p r e s e n t e d to p r o v i d e e x a m p l e s of t h e v a r i a b i l i t y t h a t e x i s t s i n t h e c l i n i cal s e v e r i t y o f t h i s d i s e a s e .
A RESTRICTION fragment length polymorphism within the long arm of h u m a n c h r o m o s o m e 3 h a s b e e n l i n k e d to t h e d i s e a s e t r a i t in a l a r g e family in I r e l a n d w i t h a u t o s o m a l d o m i n a n t r e t i nitis pigmentosa.' Since the rhodopsin gene a l s o m a p s to t h e l o n g a r m o f c h r o m o s o m e 3^·^ a n d s i n c e r h o d o p s i n is e x p r e s s e d in r o d p h o t o -
Accepted for publication Feb. 18, 1991. From the Berman-Gund Laboratory for the Study of Retinal Degenerations and the Howe Laboratory of Oph thalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts. This study was supported in part by National Eye Institute grants EY00169 and EY02014 and grants from the Na tional Retinitis Pigmentosa Foundation, Baltimore, Maryland, and the George Gund Foundation, Cleveland, Ohio. Dr. Berson is a Research to Prevent Blindness Senior Scientific Investigator. Reprint requests to Eliot L. Berson, M.D., Massachu setts Eye and Ear Infirmary, 243 Charles St., Boston, MA 02114.
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r e c e p t o r s t h a t are a f f e c t e d e a r l y in t h i s d i s ease,^* w e h a v e b e e n s e a r c h i n g for a b n o r m a l i t i e s in t h e r h o d o p s i n g e n e in t h e l e u k o c y t e DNA o f p a t i e n t s w i t h d o m i n a n t r e t i n i t i s p i g mentosa. We p r e v i o u s l y d e s c r i b e d f o u r d i s t i n c t p o i n t m u t a t i o n s in t h e g e n e c o d i n g for r h o d o p s i n . " ' O f 1 4 8 unrelated patients from separate fami l i e s r e s i d i n g in t h e U n i t e d S t a t e s o r C a n a d a with autosomal dominant retinitis pigmentosa, 2 7 c a r r y o n e o f t h e s e four m u t a t i o n s . E a c h mutation corresponds to a single a m i n o acid s u b s t i t u t i o n in t h e r h o d o p s i n p r o t e i n . T h e s e rhodopsin mutations and their frequencies by f a m i l y a r e as f o l l o w s : p r o l i n e - 2 3 - h i s t i d i n e , 1 7 cases ( 1 2 % ) ; proline-347-leucine, eight cases (5%); proline-347-serine, one case ( 0 . 5 % ) ; and threonine-58-arginine, one case ( 0 . 5 % ) . Only o n e m u t a t i o n h a s b e e n f o u n d in a n y g i v e n family, and each mutation h a s segregated per f e c t l y w i t h t h e d i s e a s e trait in t h e f a m i l i e s s t u d i e d . W e h a v e n o t o b s e r v e d t h e s e m u t a t i o n s in 106 unrelated normal individuals. T h e s e results suggest that these mutations are the cause o f some forms o f dominant retinitis pigmentosa."' We s t u d i e d t h e o c u l a r findings i n e i g h t u n r e lated patients with dominant retinitis pigmen tosa and rhodopsin, proline-347-leucine. Their findings are c o m p a r e d with those from 1 4 0 patients without this mutation. We also studied e i g h t r e l a t i v e s from t h r e e o f t h e s e f a m i l i e s to show the range of abnormalities that exists among patients with this mutation.
Patients and Methods We r e v i e w e d t h e c l i n i c a l findings o f 1 4 8 p a tients, ages 1 8 to 4 9 years, with autosomal dominant retinitis pigmentosa who had donat ed a b l o o d s p e c i m e n for m o l e c u l a r g e n e t i c s t u d ies o f t h e i r l e u k o c y t e D N A . A l l 1 4 8 p a t i e n t s
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Rhodopsin, Proline-347-Leucine
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TABLE 1 FINDINGS ON HISTORY IN AFFECTED PATIENTS CASE NO., FAMILY NO., AGE (YB8), SEX
AGE OF ONSET OF NIGHT BLINDNESS (YB8)
AGE OF ONSET OF DIFFICULTY WITH SIDE VISION (YRS)
1,6003,22, Μ 2, 3570, 25, Μ 3, 0140, 30, Μ 4, 6073, 31, F 5, 5683, 32, F 6, 5864, 35. F 7,0771,35, Μ 8, 6473, 45, Μ
14 12 Near birth 8 13 16 6 18
14 20 12 16 27 22 23 21
w e r e from s e p a r a t e families a n d resided in t h e U n i t e d States o r C a n a d a . E a c h p a t i e n t w a s from a family with a d o m i n a n t m o d e of t r a n s m i s s i o n of retinitis p i g m e n t o s a o v e r at least t h r e e c o n secutive g e n e r a t i o n s . E i g h t of t h e s e p a t i e n t s had a cytosine-to-thymine transition heterozygously in t h e s e c o n d n u c l e o t i d e b a s e of c o d o n 3 4 7 ( c y t o s i n e - c y t o s i n e - g u a n i n e to c y t o s i n e - t h y mine-guanine) corresponding to a substituton of l e u c i n e for p r o l i n e , w h e r e a s 1 4 0 of t h e s e p a t i e n t s did n o t h a v e this m u t a t i o n . ' All 1 4 8 patients had retinal arteriolar narrowing; most h a d i n t r a r e t i n a l b o n e spicule p i g m e n t a t i o n . W e also r e v i e w e d the o c u l a r findings in eight clini
cally affected r e l a t i v e s of t h r e e of t h e eight p a t i e n t s w i t h this m u t a t i o n . T h e s e relatives were selected because they had already provid e d b l o o d s p e c i m e n s for D N A a n a l y s i s ; all e i g h t relatives a l s o h a d t h e s a m e c y t o s i n e - t o - t h y m i n e t r a n s i t i o n in t h e s e c o n d n u c l e o t i d e b a s e of c o d o n 3 4 7 of t h e r h o d o p s i n g e n e . All eight p a t i e n t s w i t h this m u t a t i o n h a d E u r o p e a n family origin w i t h n o single c o u n t r y p r e d o m i n a t i n g . T h r e e r e s i d e in N e w E n g l a n d , t w o in t h e m i d - A t l a n t i c s t a t e s , a n d t h r e e in midwestern states. T h e 1 4 8 p a t i e n t s w i t h d o m i n a n t r e t i n i t i s pig mentosa completed a questionnaire regarding t h e a g e of o n s e t o f n i g h t b l i n d n e s s a n d a g e of o n s e t of difficulty w i t h s i d e o r p e r i p h e r a l vi sion. W e e v a l u a t e d their d i s t a n c e S n e l l e n a n d F e r r i s visual a c u i t i e s , k i n e t i c G o l d m a n n visual fields, i n t r a o c u l a r p r e s s u r e b y a p p l a n a t i o n t o n o m e t r y , d a r k - a d a p t e d full-field e l e c t r o r e t i n o g r a m s , r e t i n a l visual a c u i t i e s , s l i t - l a m p a p p e a r ance of e a c h lens, and fundus a p p e a r a n c e by o p h t h a l m o s c o p y a s d e s c r i b e d p r e v i o u s l y . ' Slitlamp examination was performed to determine p r e s e n c e or a b s e n c e o f a c e n t r a l p o s t e r i o r s u b c a p s u l a r c a t a r a c t in e a c h eye. O p h t h a l m o s c o p i c examination was performed to determine w h e t h e r or n o t c y s t o i d m a c u l a r e d e m a c o u l d be s e e n a n d w h e t h e r i n t r a r e t i n a l b o n e s p i c u l e pig m e n t w a s in the p e r i p h e r y in all f o u r q u a d r a n t s .
TABLE 2 FINDINGS ON OCULAR EXAMINATION IN AFFECTED PATIENTS
VISUAL ACUITY CASE NO., AGE (YRS)
1,22 2, 25 3,30 4, 31 5,32 6,35 7,35 8,45
EYE
SNELLEN
FERRIS*
RETINAL
R.E. L.E. R.E. LE. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E. R.E. L.E.
20/27 20/30 20/85 20/82 20/20 20/20 20/21 20/21 20/33 20/52 20/37 20/41 20/37 20/30 20/93 20/42
54 47 24 31 59 59 58 58 50 39 44 41 44 47 31 42
20/33 20/37 20/112 20/120 20/20 20/24 20/20 20/20 20/36 20/42 20/37 20/34 20/25 20/25 20/102 20/47
REFRACTIVE ERROR
+0.50 -1.25 X 95 +0.50 -1.75 X 80 +2.00 -1.50 X 172 +3.00 -1.87 X 170 +0.87 -0.87 X 15 +0.87 -1.12 X 160 -1.37 -0.62 X 7 -1.75 -1.00 X 180 +0.87 -2.50 X 15 +0.50 -3.00 X 177 -0.62 -0.50 X 22 +0.37 -3.25 -0.62 X 60 -3.37 -0.50 X 150 + 1.25 -0.75 X 157 +0.75 -1.25 X 177
•Number of letters read; 65 letters equals Snellen equivalent of 20/20.
LENS
Clear Clear Posterior subcapsular opacity Posterior subcapsular opacity Clear Clear Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity Posterior subcapsular opacity
INTRARETINAL BONE SPICULE PIGMENT IN FOUR QUADRANTS
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
616
May, 1991
AMERICAN JOURNAL OF OPHTHALMOLOGY
V i s u a l fields w e r e p l o t t e d w i t h a d i g i t i z i n g t a b l e t , a n d the t o t a l a r e a for e a c h e y e w a s q u a n t i f i e d b y a c o m p u t e r in s q u a r e d e g r e e s a n d e x p r e s s e d a s a n e q u i v a l e n t c i r c u l a r a r e a or equivalent circular diameter. Electroretino g r a m s w e r e q u a n t i f i e d w i t h r e s p e c t to p e a k - t o p e a k a m p l i t u d e s for t h e m i x e d c o n e - r o d r e s p o n s e s t o 0 . 5 - H z w h i t e flashes, t h e c o n e - i s o l a t e d r e s p o n s e s to 3 0 - H z w h i t e flashes, a n d t h e 3 0 - H z c o n e b-wave implicit times (that is, the t i m e i n t e r v a l s b e t w e e n e a c h flash o f l i g h t a n d t h e c o r r e s p o n d i n g c o r n e a - p o s i t i v e p e a k ) as d e scribed previously.' T h e data derived from ocular e x a m i n a t i o n s o f the 1 4 8 patients with d o m i n a n t retinitis pig mentosa were coded by one person and checked b y a n o t h e r ; data w e r e t h e n k e y p u n c h e d , v e r i fied, a n d s t o r e d on a m a g n e t i c t a p e for d a t a p r o c e s s i n g . D a t a w e r e t h e n v a l i d a t e d for e r r o r s a n d i n c o n s i s t e n c i e s a n d c o r r e c t e d as n e c e s s a r y . Comparisons were made between the group of eight unrelated patients with this mutation and the group of 1 4 0 unrelated patients without this mutation. Each o f the 1 4 8 patients was e x a m i n e d t w i c e w i t h i n s i x w e e k s , a n d a n aver a g e s c o r e for e a c h e y e w a s c o m p u t e d for e a c h test p a r a m e t e r . F o r t h e p u r p o s e o f s t a t i s t i c a l a n a l y s i s , a n a v e r a g e o f t h e s e s c o r e s for t h e t w o eyes was used. Since the distributions o f S n e l len distance visual acuities, retinal visual acui t i e s , v i s u a l field e q u i v a l e n t c i r c u l a r a r e a s , a n d electroretinogram amplitudes were skewed, the data w e r e t r a n s f o r m e d u s i n g t h e log^ s c a l e to a p p r o x i m a t e b e t t e r a n o r m a l d i s t r i b u t i o n for e a c h p a r a m e t e r for p u r p o s e s o f s t a t i s t i c a l a n a l ysis. D a t a for c o n t i n u o u s v a r i a b l e s , s u c h as best-corrected visual acuity or spheric refrac tive e r r o r , w e r e a n a l y z e d u s i n g f-tests for u n i v a r i a t e a n a l y s e s . ' " D i s c r e t e v a r i a b l e s , s u c h as p r e s e n c e or a b s e n c e o f p o s t e r i o r s u b c a p s u l a r c a t a r a c t in b o t h e y e s or p r e s e n c e or a b s e n c e o f b o n e s p i c u l e p i g m e n t in all f o u r q u a d r a n t s o f t h e f u n d u s p e r i p h e r y in b o t h e y e s , w e r e a n a l y z e d w i t h t h e Y a t e s c o r r e c t e d c h i - s q u a r e test or F i s h e r ' s e x a c t test.'" A g e o f o n s e t o f n i g h t b l i n d n e s s a n d a g e o f o n s e t o f difficulty w i t h s i d e vision were evaluated by using the log-rank life-table m e t h o d o f analysis; patients w h o did n o t yet h a v e n i g h t b l i n d n e s s or w h o h a d n o t yet r e p o r t e d v i s u a l field l o s s w e r e t r e a t e d a s c e n sored observations with the length of the f o l l o w - u p p e r i o d e q u a l to t h e i r c u r r e n t a g e . " Multiple regression analysis used group m e m bership, age, and sex as the independent varia b l e s a n d s e l e c t e d o c u l a r findings a s t h e d e p e n dent variables. This allowed assessment of
TABLE 3 VISUAL FIELDS A N D ELECTRORETINOGRAMS IN A F F E C T E D PATIENTS
ELECTRORETINOGRAM'
VISUAL FIELD* C A S E NO.,
0.5-H2
30-HZ
30-HZ
AMPLI
AMPLI
IMPLICIT
TUDE
TUDE
TIME
A G E (YRS)
EYE
AREA
DIAMETER
(MV)
(MV)
(MSEC)
L22
R.E. L.E. R.E. LE. R.E. L.E. R.E. LE. R.E. LE. R.E. LE. R.E. L.E. R.E. LE.
7194 6742 384 326 2197 2222 2718 3052 2075 1992 186 189 1658 1773 484 536
96 93 22 20 53 53 59 62 51 50 15 15 46 47 25 26
3.3 2.9 1.2 1.7 1.8 3.0 3.2 2.7 1.6 1.6 1.1 NA* 1.0 1.3 1.0 1.0
1.1 1.4 1.0 1.1 1.0 1.2 0.7 0.6 0.2 0.2 0.2 0.2 0.7 0.6 0.3 0.3
47 48 42 43 40 41 39 41 34 34 43 47 35 34 33 34
2,25 3, 30 4, 31 5,32 6,35 7,35 8,45
*Area is ttie visual field area Including periptieral islands in degrees squared to a V«, white test light. Lower limit of normal is 11,399 degrees squared. Diameter is equivalent circular diame ter in degrees: 2 V ^ . •Full-field electroretinograms: normal limits are 0.5-Hz white > 350 MV; 30-Hz white flicker s 50 μΨ, and 30-Hz b-wave implicit time s 32 msec. «NA indicates not available.
differences b e t w e e n the two groups for selected o c u l a r findings after c o r r e c t i n g f o r a g e a n d sex.'" We e x a m i n e d eight affected relatives from three of the families o n c e . Their clinical findings p r o v i d e a d d i t i o n a l d a t a o n t h e r a n g e o f ocular abnormalities seen in patients with this mutation and show examples of some variabili ty o f c l i n i c a l e x p r e s s i o n o f t h i s c o n d i t i o n among patients of comparable age.
Results T h e e i g h t p a t i e n t s from s e p a r a t e f a m i l i e s with dominant retinitis pigmentosa and rhodopsin, p r o l i n e - 3 4 7 - l e u c i n e reported s o m e var i a b i l i t y in t h e a g e o f o n s e t o f n i g h t b l i n d n e s s (Tables 1 through 3 ) . For example, one patient
Vol. I l l , No. 5
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Rhodopsin, Proline-347-Leucine
TABLE 4 GROUP COMPARISONS OF PATIENTS WITH (GROUP 1) AND WITHOUT (GROUP 2) PROLINE-347-LEUCINE RHODOPSIN MUTATION
PARAMETERS
GROUP 1 (N = 8)
GROUP 2 (N = 140)·
f-STAT
RVALUE
Ρ VALUE (CORRECTED)'
Snellen* visual acuity Ferris visual acuity Retinal* visual acuity Spheric refractive error Cylindric refractive error Intraocular pressure (mm Hg) Visual field area (deg^ 0.5-Hz electroretinogram (/tV)* 30-Hz electroretinogram (/tV)* 30-Hz electroretinogram (msec)
+0.61 ± 0.49 (20/37)
+0.54 ± 0.54 (20/34)
+0.33
NS
NS
-0.92
NS
NS
+45.28 ± 10.48
+48.36 ± 9.16
+0.64 ± 0.59 (20/38)
+0.48 ± 0.40 (20/32)
+1.08
NS
NS
+0.07 -1.19 12.16 7.11 0.52 -0.62 39.44
-0.21 -1.16 11.92 7.99 1.79 +0.65 42.22
+0.21 +0.10 +0.31 -1.84 -6.57 -4.27 -1.73
NS NS NS NS
