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December 2007

The GLC1H Glaucoma Locus May Reflect Glaucoma With Elevated Intraocular Pressure

Arch Ophthalmol. 2007;125(12):1716-1717. doi:10.1001/archopht.125.12.1716-b

We read with interest the recent article by Suriyapperuma et al1 on the identification of a new locus (GLC1H) for adult-onset primary open-angle glaucoma to chromosome 2p15-p16. They performed genetic linkage analysis on 49 members of a single family, with 10 affected individuals with glaucoma. The patients with glaucoma each had moderate to high intraocular pressure (IOP) in at least 1 eye (IOP > 22 mm Hg [range, 22-40 mm Hg]) prior to treatment. Suriyapperuma and colleagues identified a maximum logarithm of the odds (LOD) score at marker D2S370 (LOD = 2.97). Additional families refined this locus and the LOD score increased to 9.30 at D2S2320. We are intrigued because in our recent genetic linkage analysis of IOP in the Beaver Dam Eye Study,2 we also identified a peak in this same region on chromosome 2. Using Haseman-Elston regression of sibling pairs, we performed nonparametric linkage analysis of 1979 individuals from 486 pedigrees and identified the maximum peak near marker D2S1777 (with an empirical P value of .007) approximately 17 cM from the GLC1H peak. The 1-LOD drop interval of our peak coincides with the GLC1H locus. Because the glaucoma cases in the study by Suriyapperuma and colleagues had moderate to high IOP, our findings together suggest that this locus may be controlling glaucoma resulting from elevated IOP. Future genetic studies of this region should specifically analyze the subset of patients with glaucoma with ocular hypertension to test this hypothesis.

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