A 33-Year-Old Woman with Blanching on Her Lower Legs

Differential Diagnosis

• Cellulitis
• Erysipelas
• Erythema multiforme
• Erythema nodosum

Diagnosis

This patient was diagnosed with erythema nodosum (EN), the most common type of inflammatory panniculitis (inflammation of the fat). This is an inflammatory process, typically symmetrical, and located on the pretibial region. It represents a form of hypersensitivity reaction precipitated by infection, pregnancy, medications, connective tissue disease, or malignancy; often, however, a trigger is never found. 

Learnings/What to Look for

• Eruptions typically persist for 3-6 weeks and spontaneously regress without scarring or atrophy
• Recurrences are sometimes seen, especially with reoccurrence of the precipitating factors
• Arthralgias are reported by a majority of patients, regardless of the etiology of EN
• Upper respiratory tract infection or flu-like symptoms may precede or accompany the development of the eruption
• EN can occur at any age, but most cases occur between the ages of 20 and 45, particularly in women

Pearls for Urgent Care Management and Indications for Transfer

• EN is self-limited, though antibiotics may be indicated to treat underlying infection
• If the nodules are painful, nonsteroidal anti-inflammatory medications may also be helpful

Acknowledgment: Images and case courtesy of VisualDx (www.VisualDx.com/JUCM).