Multipoint linkage analysis allowing for locus heterogeneity was performed for the SHAS phenotype using microsatellite and SNP data from 10qter. The family specific heterogeneity score (α) and LOD score was inspected for each family. Most of the families had α scores of 0.99, one family stood out with an α of 0.37 indicating poor support for linkage to the region. The individual pedigree LOD score for this family alone was −0.97 accounting for most of the reduction in LOD score seen between stage 1 and stage 2. Based on the level of alleles shared between siblings in this family, it was expected that these siblings should have more similar SHAS scores. The sibling pair had a large difference in phenotype despite having inherited the same chromosome Identical By Descent from both of their parents (IBD of 2). While one sibling reported a SHAS score of 26.75 (z = 2.147), the other reported a SHAS score of 4 (z = −0.7161).
