Differential Diagnosis for a Toddler with a Purple Head of Penis

• Single most likely diagnosis:
  • Physiological smegma or normal penile anatomy: In toddlers, the head of the penis can sometimes appear purple due to normal anatomical variations or the presence of smegma, a substance that accumulates under the foreskin. This condition is benign and does not require medical intervention.
• Other Likely diagnoses:
  • Balanitis: An inflammation of the glans penis, which can be caused by infection, irritation, or poor hygiene. It's common in uncircumcised males and can present with redness, swelling, and sometimes a purplish discoloration.
  • Contact dermatitis or irritant dermatitis: This can occur due to exposure to soaps, detergents, or other substances that irritate the skin, leading to redness, swelling, and possibly a purplish hue.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
  • Testicular torsion or epididymitis: Although these conditions primarily affect the testicles, severe cases can lead to changes in penile color due to compromised blood flow. These are medical emergencies requiring immediate attention.
  • Paraphimosis: A condition where the foreskin is retracted behind the glans penis and cannot return to its original position, potentially cutting off blood flow and leading to ischemia, which could cause a purplish discoloration.
• Rare diagnoses:
  • Henoch-Schönlein purpura (HSP): A form of vasculitis that can cause purpura (bleeding under the skin), which might be visible on the penis, though this is less common. HSP is characterized by a tetrad of symptoms: abdominal pain, joint pain, kidney involvement, and the purpuric rash.
  • Malignancies: Extremely rare in toddlers, but certain types of cancer, like sarcomas or lymphomas, could potentially present with unusual skin discolorations, including purple lesions on the penis.