Moreover, when comparing different gPrD cases with low CSF tau (<1400 pg/ml) to non-PrD cases also exhibiting low CSF tau, significantly higher ratios of CaM positivity were found in the group of T188K-gCJD, E200K-gCJD, and P102L-GSS, but not in that of D178N-FFI. The gene discussed is MAPT; the disease is X-linked retinal dysplasia.