HEPHL1 and attention deficit-hyperactivity disorder: In this study, we demonstrate a potential physiological role for HEPHL1 based upon two different pathogenic HEPHL1 mutations found in a patient who clinically presented with abnormal hair (pili torti and trichorrhexis nodosa), combined-type attention deficit hyperactivity disorder (ADHD), speech articulation disorder, increased joint mobility, severe heat intolerance, and chronic leg pain.