Familial aggregation of severity of diabetic retinopathy in Mexican Americans from Starr County, Texas.
OBJECTIVE
Diabetic retinopathy is a major cause of blindness. To determine whether retinopathy itself or only its severity aggregates in families, we examined the occurrence and severity of diabetic retinopathy in Mexican-American siblings with type 2 diabetes.


METHODS
Using stereoscopic fundus photography of seven standard fields, we measured retinopathy in 656 type 2 diabetic patients from 282 Mexican-American families from Starr County, Texas. Retinopathy severity was scored using the Early Treatment of Diabetic Retinopathy Study system and classified as no retinopathy, early nonproliferative diabetic retinopathy (NPDR-E), moderate-to-severe nonproliferative diabetic retinopathy (NPDR-S), or proliferative diabetic retinopathy (PDR).


RESULTS
Of 249 siblings of randomly selected probands with retinopathy, 169 (67.9%) had retinopathy, compared with 95 of 125 siblings of unaffected probands (76.0%; P = 0.11). Proband retinopathy class was associated (P = 0.03) with sibling retinopathy class, with significant odds ratios (ORs) for NPDR-E versus no retinopathy (OR 0.57 [95% CI 0.35-0.93]) and PDR versus NPDR-E (2.02 [1.13-3.63]); the contrast of NPDR-S versus NPDR-E approached significance (1.78 [0.99-3.20]). With the more severe classes (PDR and NPDR-S) combined in one group and the less severe ones (none and NPDR-E) in another, more severe proband retinopathy was associated with more severe sibling retinopathy (1.72 [1.03-2.88]).


CONCLUSIONS
More severe diabetic retinopathy showed evidence of familial aggregation, but the occurrence of diabetic retinopathy per se did not. The factors involved in the onset of diabetic retinopathy may differ from those involved in its progression to more severe forms.
Hallman
D Michael
DM
Human Genetics Center, The University of Texas Health Science Center at Houston, P.O. Box 20186, Houston, TX 77225, USA.
Huber
J Charles
JC
Gonzalez
Victor H
VH
Klein
Barbara E K
BE
Klein
Ronald
R
Hanis
Craig L
CL
D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000208:ethnology* / Q000235:genetics; D003930:Diabetic Retinopathy / Q000208:ethnology* / Q000235:genetics; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D017058:Mexican Americans / Q000706:statistics & numerical data*; D008875:Middle Aged; D015995:Prevalence; D012720:Severity of Illness Index; D035781:Siblings; D013781:Texas / Q000453:epidemiology