Members in three generations of a family whose propositus had keratoconus were examined by biomicroscopy, with a corneoscope and a computer-assisted videophotokeratoscope. Keratoconus was detected in eight of 15 family members with vertical transmission consistent with autosomal dominant inheritance. Affected individuals displayed variable topographic features. Abortive 'nipple-type' cones were identified in some individuals in successive generations using the computer-assisted videophotokeratoscope and more advanced nipple-type cones detected on biomicroscopy of other family members. We selected a COL6A1 cDNA (the gene encoding the α1 chain of type VI collagen) as a 'candidate gene' to determine cosegregation with the disease locus. Linkage analysis excluded a gene locus for keratoconus on the most telomeric region of chromosome 21 in this family.
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