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A. Ramirez-Miranda, H. Perez-Cano, J. C. Zenteno; Linkage to Locus 13q31-32 in a Mexican Family Affected by Autosomal Dominant Congenital Microcoria. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1300.
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Autosomal dominant congenital microcoria (CMC) also called congenital miosis, is a rare disorder due to a maldevelopment of the dilator pupillae muscle of the iris, and it is characterized phenotypically by pupil diameter less than 2mm, iris hypopigmentation and, transillumination. Affected individuals have no response to topically administered mydriatic drugs. CMC is associated with juvenile open angle glaucoma and myopia. Linkage analysis in French and Asian Indian pedigrees indicated that the responsible gene is located in the chromosomal locus 13q31-q32. In this study we report the results of genetic linkage analysis in a Mexican family with autosomal dominant CMC.
A Two generation family of Mexican-mestizo origin was studied. The proband was a healthy 13 years old male with microcoria since birth, complaining of nyctalopia and blurred vision, his father was affected by the same ocular anomaly while the mother and 2 siblings were healthy. All of them underwent full ophthalmologic examination. Pupil and Iris features were measured by ultrabiomicroscopy.PCR based microsatellite marker genotyping was performed using dinucleotide fluorescent markers linked to chromosome 13: D13S170, D13S265, D13S1300, D13S281, D13S154, D13S1280, D13S1241,D13S159. The alleles were genotyped using Genescan software.
Opthalmologic and ultrabiomicroscopic examination confirmed the diagnosis of MCM in the two affected individuals.Microsatellite marker genotyping indicated that the father and his affected son shared a common 13q31-32 haplotype from marker D13S170 (centromeric) to D13S159 (telomeric).The two unaffected sibs inherited from their father a different haplotype. There was no recombination in the markers in the alles from our patients.
This is the first clinical description and the first genetic linkage analysis in a family with autosomal dominant CMC in Latin America. Despite of the small size of this family, our data supports genetic homogeneity for 13q31-32 as the locus carrying the causal gene of CMC.
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