Clinical features

A prodrome of weight loss, malaise, low-grade fever, cough, and arthralgia with or without arthritis may be seen one to three weeks before the onset of the disease (1,2)

Characteristically the lesions are:

• painful, palpable, dusky blue nodules or plaques:
  • may vary from 1-10 cm in diameter
  • poorly demarcated
  • most commonly on the shins and calves
  • may spread to the thighs and extensor surfaces of the forearm and the trunk
  • tend to be symmetrical
  • initially the nodules are firm but becomes more fluctuant as the disease progress
• lesions resolve completely over 1-2 months and may produce to produce an appearance similar to bruising as they fade
• ulceration of the nodules cannot be seen and usually heal without atrophy or scarring
• there may be the appearance of new lesions as the old ones resolve

Arthralgia produced during the prodrome period has been known to continue for up to 2 years after the resolution of the disease and may cause nonspecific destructive changes in the joint.

References:

1. Requena L, Requena C. Erythema nodosum (review). Dermatol Online J. 2002 Jun;8(1):4.
2. Perez-Garza D et al. Erythema Nodosum: A Practical Approach and Diagnostic Algorithm. Am J Clin Dermatol. 2021 May;22(3):367-378