pestis transmitted via flea bites carries a high mortality and is rare in the United States Bubonic plague, the most common form, causes regional exquisitely tender lymphadenitis (bubo) with overlying erythema in the area of the bite, and the inguinal nodes are the most common site Ulceroglandular tularemia is transmitted by tick bites and can cause inguinal adenopathy and adenitis that often precede the appearance of a small papule that later ulcerates at the portal of entry on the lower extremity Both plague and tularemia exist in pneumonic forms that have become agents of bioterrorism (see Chapter 132 Biological and Chemical Terrorism ) Filariasis, a parasitic disease transmitted by fly or mosquito bites and found in the tropics, can produce adenopathy or adenitis associated with lower extremity lymphedema and scrotal pathology Treatment is dependent on the extent of disease (see treatment options in Table 39.2 ) TABLE 39.1 CAUSES OF INGUINAL MASSES Painful a Torsion of an undescended testicle a Trauma (e.g., dislocated testicle, hematoma) a Incarceration or strangulation of an indirect or direct inguinal hernia a Herniation of the ovary and/or fallopian tube Lymphadenitis (+/− suppurative) Hidradenitis suppurativa Usually or comparatively painless Hernia (intermittent, reducible) Lymphadenopathy Tumor, benign or malignant Retractile or undescended testicle Hydrocele of the spermatic cord a Urgent or emergent condition Sexually transmitted infections can result in inguinal adenopathy or adenitis (see Chapter 92 Gynecology Emergencies ) Herpes simplex is a common cause of genital ulcerations and bilateral lymphadenitis Occasionally, enlarged lymph nodes precede the appearance of vesicles The chancre of primary syphilis is painless and has a raised, indurated border and a clean surface Bilateral (70%) or unilateral, nontender inguinal adenopathy is common Chancroid, more common