Psoriatic Onycho-Pachydermo-Periostitis.

Psoriatic onycho-pachydermo-periostitis (POPP) is an unfamiliar and poorly recognised condition first described in 1989 by Fournie et al. It is a variant of psoriatic arthritis comprising the triad of onycholysis, soft tissue thickening and radiographically apparent periostitis. Whilst typically affecting the great toe, any of the digits of the hands and feet may be affected. A 'drumstick' appearance to the digits of the foot is the most common clinical presentation and can be extremely painful. Nail changes are another hallmark of POPP and can be mistakenly diagnosed as fungal infection leading to lengthy periods of incorrect treatment. In this article, we will outline the clinical presentation, imaging features, pathogenesis and treatment options for POPP. Currently, the existence of POPP is not widely known. Awareness of this unusual condition will allow early appropriate treatment and can aid in the diagnosis of indeterminate seronegative disease.