Differential Diagnosis for Erythematous Urethra Tip in a 41-Year-Old Male

Single Most Likely Diagnosis

• Prostatitis: This condition, particularly chronic prostatitis/chronic pelvic pain syndrome, is a common cause of pain on ejaculation and urination in men. The erythematous urethra tip could be secondary to inflammation or infection, even if initial STI labs are negative, as some cases might not be due to common STIs.

Other Likely Diagnoses

• Urethritis: Despite negative STI labs, urethritis (inflammation of the urethra) could still be a consideration, especially if the labs were done early in the course of the disease or if the causative agent is not commonly tested for (e.g., certain bacteria or viruses).
• Meatal Stenosis: This condition, characterized by narrowing of the urethral meatus, can cause pain during urination and could potentially lead to an erythematous appearance due to chronic irritation or inflammation.
• Interstitial Cystitis: A condition causing bladder pressure, bladder pain, and sometimes pelvic pain, which could indirectly cause discomfort during ejaculation and urination, though it less commonly presents with an erythematous urethra tip.

Do Not Miss Diagnoses

• Cancer (e.g., Prostate, Urethral): Although rare, it's crucial not to miss a diagnosis of cancer, as it can present with similar symptoms, including pain during urination or ejaculation and changes in the urethral appearance.
• Tuberculosis (TB) of the Genitourinary Tract: TB can affect the genitourinary system and present with symptoms like those described, including sterile pyuria (pus in the urine with negative culture), which might not be initially identified on standard U/A and STI labs.

Rare Diagnoses

• Reiter's Syndrome (Reactive Arthritis): A form of arthritis that occurs in reaction to an infection elsewhere in the body, often in the intestines or the urinary tract. It can cause urethritis, among other symptoms.
• Behçet's Disease: A rare disorder that causes blood vessel inflammation throughout the body, which can lead to a variety of symptoms including genital ulcers and potentially urethral inflammation.
• Sjögren's Syndrome: An autoimmune disorder that can cause inflammation in various parts of the body, including the genitourinary system, though it's less commonly associated with the specific symptoms described.