[1] Univ Michigan, Sch Med, Dept Dermatol, Ann Arbor, MI 48109 USA
[2] Univ Michigan, Ctr Stat Genet, Dept Biostat, Ann Arbor, MI 48109 USA
[3] Univ Calif San Francisco, Dept Neurol, San Francisco, CA 94143 USA
[4] Univ Michigan, Dept Computat Med & Bioinformat, Ann Arbor, MI 48109 USA