| Primary (idiopathic) |
| Secondary |
| Hematologic (sickle cell disease, leukemia, thalassemia, multiple myeloma, thrombotic thrombocytopenic purpura) |
| Neurologic (spinal shock) |
| Malignancy (metastatic cancer) |
| Perineal, pelvic, or penile trauma |
| Iatrogenic (intracavernous injections) |
| Drugs (anticoagulants, antihypertensives, antidepressants, PDE5 inhibitors, intracavernous injections, alpha-blockers, methylphenidate, atomoxetine, cocaine) |
| Infection (malaria, spider toxins) |
| Metabolic disorders (gout, hemodialysis, high lipid content, total parenteral nutrition, diabetes mellitus, amyloidosis) |
