Rare disorders of penile erection.

This literature review presents two unusual and mystifying disorders of penile erection: painful nocturnal erections, alternatively termed sleep-related painful erections, and idiopathic stuttering priapism, a variant of recurrent ischemic priapism in which no cause is discernible. The disorders are closely related although they are distinct clinically and pathologically. The main subject areas of discussion are recognition, clinical evaluation and management although current concepts surrounding their causes and mechanisms are also addressed. It is acknowledged that despite the perceived rarities of these disorders they are impactful in terms of their disease profiles and consequences. Future advances in their management will require continued development of evidence-based treatments.