Reduced fractional anisotropy (FA) in LND patients relative to LNV, LND < LNV. Unthresholded tract-based spatial statistics (TBSS) results for LND < LNV. Green is the skeleton, with shades of orange and red representing areas of white matter tracts of FA differences. HC, healthy control; LND, Lesch–Nyhan disease; LNV, Lesch–Nyhan variant