Differential Diagnosis for Priapism

Priapism is a medical emergency characterized by a prolonged and painful erection of the penis, often unrelated to sexual desire or stimulation. The following differential diagnosis categorizes potential causes of priapism, with a focus on psychiatric medications that can induce this condition.

• Single Most Likely Diagnosis
  • Antipsychotic-induced priapism: Certain antipsychotic medications, particularly those with alpha-adrenergic blocking properties (e.g., chlorpromazine, risperidone), can cause priapism. This is due to their effect on the alpha-adrenergic receptors in the penis, which can lead to unregulated blood flow and prolonged erection.
• Other Likely Diagnoses
  • Antidepressant-induced priapism: Some antidepressants, especially those with serotonergic and alpha-adrenergic blocking effects (e.g., trazodone), can cause priapism. The mechanism is similar to that of antipsychotics, involving the disruption of normal penile blood flow regulation.
  • Sildenafil and other phosphodiesterase type 5 (PDE5) inhibitors misuse: While PDE5 inhibitors are used to treat erectile dysfunction, their misuse or use in excessive doses can lead to priapism.
• Do Not Miss Diagnoses
  • Sickle cell disease: A condition that can cause priapism due to sickling of red blood cells within the penile vasculature, leading to obstruction and prolonged erection. This condition is critical to identify as it requires specific management to prevent long-term damage.
  • Leukemia: Certain types of leukemia can cause priapism by infiltrating the penile vasculature or by inducing a hypercoagulable state, leading to venous thrombosis within the penis.
• Rare Diagnoses
  • Fabry disease: A rare genetic disorder that can lead to priapism due to the accumulation of globotriaosylceramide in the vascular endothelium, affecting blood flow regulation.
  • Spinal cord injury or disease: Conditions affecting the spinal cord, such as spinal cord injury, tumors, or multiple sclerosis, can disrupt the normal neural control of erection, potentially leading to priapism.
  • Cavernosal thrombosis: A rare condition where a blood clot forms within the cavernosal bodies of the penis, leading to priapism.

Each of these diagnoses has a distinct pathophysiological basis and requires a tailored approach to management. Prompt recognition and treatment of priapism are crucial to prevent long-term erectile dysfunction and other complications.