Clinical phenotype of juvenile-onset primary open-angle glaucoma linked to chromosome 1q.

PURPOSE

Recent reports have suggested that a gene responsible for juvenile-onset primary open-angle glaucoma exists on the long arm of chromosome 1 (1q). This report describes a previously unpublished family (UM:JG3) in which juvenile-onset glaucoma is segregating in an autosomal dominant manner. The clinical features in this family were compared with those seen in other pedigrees with this condition. Linkage analysis was performed to evaluate whether a glaucoma-causing gene in UM:JG3 is linked to genetic markers on chromosome 1q.

METHODS

Affected family members, their siblings, children, and spouses were examined to identify the presence of glaucoma. Linkage studies were performed using short tandem repeat polymorphisms from chromosome 1q. Results of these studies were compared with those found for other families in which juvenile-onset primary open-angle glaucoma is linked genetically to the same chromosome 1q region.

RESULTS

The UM:JG3 family includes 22 affected individuals over five generations, including 12 still living. The average age at diagnosis for living affected individuals was 26 years. An association between myopia and glaucoma was observed in this family, but the glaucoma was not associated with iris processes or other structural anomalies. The clinical course of disease and response to treatment were similar to other families with this disease. The disease phenotype in this family is linked to markers on chromosome 1q with a maximum lod score of 3.52 at a recombination fraction of 0.00 for marker D1S433. Haplotype analysis suggests the gene responsible for glaucoma in this family is located in an 8-cM region between markers D1S445 and D1S218.

CONCLUSIONS

The glaucoma in UM:JG3 is linked to markers on chromosome 1q, with a candidate interval smaller than that in previous reports. In individuals with juvenile-onset open-angle glaucoma linked to chromosome 1q, the phenotype can range from mild ocular hypertension to blindness, resulting from marked elevations in intraocular pressure, with age at diagnosis ranging from 6 to 62 years. However, most affected individuals display a characteristic phenotype that includes onset in the first three decades of life, unusually high intraocular pressures, and the need for surgical therapy to prevent loss of vision. Whether differences in expression among families is due to allelic heterogeneity remains to be determined.