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Erythema nodosum

  • Definition

    Erythema nodosum is an inflammatory disorder that is characterized by tender, red nodules under the skin.

    Causes, incidence, and risk factors

    In about half of cases, the exact cause of erythema nodosum is unknown. Some cases may be associated with the following:

    • Infections. Some of the more common ones are:
      • Streptococcus (most common)
      • Cat scratch disease
      • Chlamydia
      • Coccidioidomycosis
      • Hepatitis B
      • Histoplasmosis
      • Leptospirosis
      • Mononucleosis (EBV)
      • Mycobacteria
      • Mycoplasma
      • Psittacosis
      • Syphilis
      • Tuberculosis
      • Tularemia
      • Yersinia
    • Pregnancy
    • Sensitivity to certain medications, including:
      • Amoxicillin and other penicillins
      • Sulfonamides
      • Sulfones
      • Oral contraceptives
      • Other antibiotics
      • Progestin

    Other associated disorders include leukemia, lymphoma, sarcoidosis, rheumatic fever, Bechet's disease, and ulcerative colitis.

    The condition is more common in women than it is in men.