Differential Diagnosis for a 17-year-old Male with Penile Swelling and Redness

Single most likely diagnosis

• Paraphimosis: This condition is characterized by the retraction of the foreskin behind the glans penis, which can lead to swelling and constriction. The presence of a band of constrictive tissue behind the glans strongly suggests this diagnosis. Paraphimosis is a urological emergency that requires prompt treatment to prevent complications such as ischemia and necrosis of the glans.

Other Likely diagnoses

• Balanitis: An inflammation of the glans penis, often caused by poor hygiene, infections (bacterial, fungal, or viral), or allergic reactions. It can present with swelling and redness of the glans.
• Phimosis: A condition where the foreskin cannot be fully retracted over the glans. While it can cause discomfort and swelling, it does not typically present with a constrictive band behind the glans.
• Sexually Transmitted Infections (STIs): Such as gonorrhea or syphilis, which can cause swelling, redness, and discharge. However, these would not typically cause a constrictive band.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed)

• Penile Fracture: Although rare and usually associated with a history of trauma, it can present with sudden swelling and pain. Missing this diagnosis could lead to severe complications.
• Necrotizing Fasciitis: A severe infection that can cause rapid progression of swelling, redness, and pain. It is a medical emergency requiring immediate attention.

Rare diagnoses

• Malignancy: Such as penile cancer, which is rare in young individuals but can present with a mass or swelling. Other rare conditions like Fabry disease or scleroderma can also affect the penis but are less likely in this context.
• Foreign Body: Insertion of a foreign body into the urethra or around the penis can cause swelling and constriction, though this would be an unusual presentation.