From the Research
The best area to take a punch biopsy from erythema nodosum is the center of a fresh, early lesion that has been present for less than 48-72 hours, as this approach maximizes diagnostic yield and helps distinguish it from other forms of panniculitis 1. When performing a biopsy, it is essential to consider the characteristics of erythema nodosum, which is primarily a panniculitis (inflammation of subcutaneous fat) 2.
- A deep incisional biopsy that includes subcutaneous fat is necessary to ensure adequate sampling of the septal panniculitis characteristic of this condition.
- The biopsy should be at least 4-6 mm in diameter and extend into the subcutaneous tissue.
- Local anesthesia (1-2% lidocaine with epinephrine) should be administered before the procedure, and the wound may require one or two sutures for closure.
- Avoid biopsying older lesions as they may show non-specific inflammation and fibrosis rather than the diagnostic septal panniculitis with granulomas and multinucleated giant cells.
- Also, avoid the periphery of lesions where diagnostic features may be less prominent, as this can lead to inaccurate diagnosis 3. The most recent and highest quality study 1 supports this approach, emphasizing the importance of early diagnosis and accurate sampling to distinguish erythema nodosum from other forms of panniculitis.
- Erythema nodosum can be the first sign of a systemic disease, and a diagnostic algorithm is proposed to optimize the initial work-up and initiate prompt and accurate management of the underlying disease 1.
- The condition is characterized by tender erythematous nodules mainly in the lower limbs on the pretibial area, and the exact cause is unknown, although it appears to be a hypersensitivity response to a variety of antigenic stimuli 1.