MAY 09, 2013
Neuro-Ophthalmology/Orbit
This study found that Coats' syndrome is a rare extramuscular complication of facioscapulohumeral muscular dystrophy type 1 (FSHD1) associated with large D4Z4 contractions. The authors conclude that closer surveillance for retinal complications is warranted in FSHD patients with D4Z4 fragments ≤ 15 kilobases (kb).
The authors investigated the frequency of Coats' syndrome and its association with D4Z4 contraction size in more than 400 patients with genetically confirmed FSHD1. The patients were found via database searches of the North American and the University of Rochester FSHD registries, via literature review, and via surveys sent to 14 FSHD referral centers in the United States and overseas.
They identified a total of 14 patients with FSHD with known genetic contraction size and Coats' syndrome: 10 from the survey and four from the literature. Thirteen of these patients were female. The median age at Coats' diagnosis was 10 years. The median D4Z4 allele fragment size was 13 kb, which the authors say is considerably smaller than the median reported in the FSHD registries.
They note that prevalent rates of retinal abnormalities for FSHD1 varied in the literature from 7 percent to 75 percent; however, only a single patient had vision loss. In addition, a Dutch population survey found 3/256 (1.7 percent) patients reporting Coats' disease. This yields a conservative range for symptomatic disease of between 0.7 percent and 1.7 percent.
They write that the predominance of females in these cases is striking given the male predominance reported in idiopathic Coats' disease, and suggests a unique, genetic and/or hormonal susceptibility of the retinal vasculature in females with FSHD1. Although other conditions lead to secondary Coats'-like syndromes, the pathologic mechanisms and clinical presentations are distinct.
They conclude that rather than patient age or disease severity, contraction size should determine the need for repeated retinal examinations in FSHD. Consequently, although they still recommend that all patients be screened for retinal vascular involvement at diagnosis, patients with large contractions should be examined annually afterward, with a low threshold for performing fluorescein angiography.