High Quality Content by WIKIPEDIA articles! Pachydermoperiostosis (PDP) or Primary hypertrophic osteoathropathy (PHO) is a rare genetic disorder that affects both bones and skin. Other names are idiopathic hypertrophic osteoarthropathy or Touraine-Solente-Gole syndrome. It is mainly characterized by pachydermia (thickening of the skin), periostosis (excessive bone formation) and finger clubbing (swelling of tissue with loss of normal angle between nail and nail bed).