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M. Siddiqui, S. Maharajan, A. Azuara–Blanco, K. Kelly, J. Dean; Testing for Myotonic Dystrophy Type 1 Gene in Pre–Senile Cataracts: Ten Years Experience . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3206.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The mutation underlying myotonic dystrophy type 1 (DM1) is linked to myotonic dystrophy protein kinase (DMPK) gene on chromosome 19q13.3. Although there are previous reports of predictive value of specific type of cataracts in the diagnosis of DM1, with the introduction of extremely specific genetic testing their added value has been questioned recently (Giordano M, 1996, Ophthalmic Research). The purpose of this study was to identify potential subtypes of cataracts that may enhance pre–test probability of DM1 gene testing in patients with pre–senile cataracts. Methods: A retrospective case control study was performed. Patients were identified from the local genetics database. Inclusion criteria were: patients aged 55 or young who were referred to the eye departments of Grampian region for cataract surgery from 1994–2003 and who subsequently had a DM1 gene testing, irrespective of the type of cataract. They were checked for expansion of unstable cytosine–thymine–guanine (CTG) trinucleotide repeats using PCR after appropriate pre–test genetic counselling. Results: A total of 340 patients were identified. Seventeen of 340 (5%) patients were found to be positive. The mean (SD) age was 45.9 (+/– 7.37) years (range, 31–54 years). Male–to–female ratio was 11:6. The frequencies of systemic findings were: ECG abnormalities (2/17), frontal balding (5/17), myotonic grip (5/17), speech problems (4/17), sleep disturbances (2/17), gastric motility problem (1/17), myotonia (1/17). Ptosis was present in 5/17 but no pigmentary retinopathy was noted in any patient. Thirty age and sex matched patients who were negative for DM1 were used as controls. Bilateral posterior subcapsular cataract (PSCC) was significantly associated with a positive DM1 gene test (odds ratio 44, 95% confidence interval 4.99 to 387.8). Conclusions: A valid significant association exists between pre–senile bilateral PSCC and an increased risk of DM1. We propose that individuals with pre–senile PSCC should be offered DM1 gene test following appropriate counselling.
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