Priapism in a young male could occur because of

Priapism is persistent ( more than 4 hours) painful erection of penis. Usually seen as a compilcation of blood disorders like leukemia, sickle cell disease. Other causes include following therapeutic injection of papaverine, abnormally prolonged bout of otherwise normal sexual activity, idiopathic thrombosis of corpora cavernosa or prostatic venous plexus, malignant disease in the corpora cavernosa or the pelvis, rarely as a consequence of spinal cord disease. Reference : page 1063 SRB's manual of surgery 5th edition and page 1374 Bailey and Love's sho practice of surgery 25th edition