TSC1 and Cockayne syndrome: Analogous to the Cockayne syndrome example in Figure 3D, this effectively converts this tuberous sclerosis testing scenario into one of locus homogeneity—because TSC2 is excluded, ∼95% of the time, a causative variant will be identified in TSC1. Therefore, the phenotype-specificity (PP4) points can be allocated to TSC1 (+7.0 points) and two non-recombinants (PP1; +2 points) for a total of +9.0 points, which would be capped at +5.0 points, before other evidence was added.