Differential Diagnosis for Multiple Painful Grouped Vesicular Lesions on Penis with Tender Inguinal Lymph Node

• Single Most Likely Diagnosis
  • Genital Herpes: This is the most likely diagnosis due to the presence of multiple painful grouped vesicular lesions on the penis, which is a classic presentation of genital herpes. The tender inguinal lymph nodes also support this diagnosis, as they often become swollen and tender during a herpes outbreak.
• Other Likely Diagnoses
  • Primary Syphilis: This condition can cause a painful genital ulcer (chancre) and tender lymph nodes, although the chancre is typically solitary and painless. However, it's essential to consider syphilis in the differential diagnosis due to its potential for serious complications if left untreated.
  • Herpes Zoster (Genital Shingles): This condition can cause a painful vesicular rash in a dermatomal distribution, which may involve the genital area. The presence of tender inguinal lymph nodes could also be seen in herpes zoster.
• Do Not Miss Diagnoses
  • Chancroid: Caused by Haemophilus ducreyi, chancroid can lead to painful genital ulcers and tender lymph nodes. Although less common in some regions, it's crucial to consider due to its potential for significant morbidity and the need for specific antibiotic treatment.
  • Lymphogranuloma Venereum (LGV): This is a sexually transmitted infection caused by certain strains of Chlamydia trachomatis. It can lead to painful lymphadenopathy and, if not treated promptly, can cause significant complications, including genital and rectal strictures.
• Rare Diagnoses
  • Becker's Melanosis or Other Dermatoses: Certain dermatological conditions can mimic the appearance of vesicular lesions but are less likely to cause the specific combination of symptoms described, including tender inguinal lymphadenopathy.
  • Autoimmune Conditions: Conditions like pemphigus or pemphigoid can cause blistering lesions but are rare and typically have other distinguishing features.

Each of these diagnoses has a distinct set of characteristics and implications for treatment, emphasizing the importance of a thorough diagnostic evaluation to guide appropriate management.