Linkage of a gene for macular corneal dystrophy to chromosome 16

Purpose. Macular corneal dystrophy (MCD) is a systemic autosomal recessive disorder involving lumican (keratan sulfate proteoglycan) with corneal accumulations leading to visual impairment. We sought to isolate the gene(s) for MCD in families from the USA and Iceland. Methods. Sixteen American and Icelandic families (eleven MCD type I and five MCD type II) were analyzed for linkage using 208 polymorphic microsatellite markers. Results. A significant LOD score of ẑ = 7.79 at θ = 0.05 was found with the 16q22 locus D16S518 for MCD type I. A LOD score of z = 2.30 @ θ = 0.00 was obtained for MCD type II using the same marker. Five of the Icelandic families could be connected into a single, highly consanguineous family containing both MCD types. Conclusions. The gene for MCD type I is located on the long arm of chromosome 16. The data are also consistent with the hypothesis that MCD type I and II arise from the same genetic locus.