Ankylosing spondylitis in a large kindred: clinical and genetic studies.

In a kindred of 66 members spanning four generations, seven cases of ankylosing spondylitis (AS) HAVE BEEN FOUND. Four of these were in a single sibship of 13. AS was associated with HL-A27 in three of the four involved siblings, but close linkage was shown to be unlikely. Knowledge of HL-A genotype has made possible informed counseling for younger members of the sibship of 13, some of whom, as teenagers, already have back pain.