Erythema Nodosum in a Young Adult: Diagnostic Workup and Management

Case at a Glance

A 25-year-old previously healthy female presents with a 2-week history of painful erythematous nodules on bilateral lower extremities, consistent with erythema nodosum. The patient has a background of non-anemic iron deficiency treated with supplementation for 3 years.

Patient's Story

The patient reported the spontaneous appearance of painful red lumps measuring 1-1.5 inches in diameter on her shin bones over a 2-week period. Approximately 5 lesions developed sequentially, initially presenting as raised, tender, erythematous nodules that subsequently evolved into flat, dark purple, non-tender areas resembling bruises. The patient denied any preceding trauma, recent infections, or new medications. She expressed concern about the unknown etiology and sought medical evaluation after researching her symptoms online.

Initial Assessment

Physical examination revealed multiple lesions on the anterior aspects of both lower legs in various stages of evolution. Active lesions presented as tender, raised, erythematous nodules measuring approximately 3-4 cm in diameter. Resolved lesions appeared as flat, hyperpigmented areas without tenderness. The patient appeared well with stable vital signs. No lymphadenopathy, joint swelling, or other systemic signs were noted.

The Diagnostic Journey

Given the clinical presentation highly suggestive of erythema nodosum, a comprehensive workup was initiated to identify potential underlying causes. Laboratory studies included complete blood count, comprehensive metabolic panel, inflammatory markers (ESR, CRP), tuberculosis screening (tuberculin skin test, chest X-ray), streptococcal antibodies (ASO, anti-DNase B), and autoimmune markers. Chest imaging was performed to rule out sarcoidosis and other pulmonary conditions commonly associated with erythema nodosum.

Final Diagnosis

Idiopathic erythema nodosum. Extensive workup failed to identify an underlying systemic cause, leading to a diagnosis of idiopathic erythema nodosum, which accounts for approximately 30-50% of cases.

Treatment Plan

Conservative management was initiated with nonsteroidal anti-inflammatory drugs (NSAIDs) for symptomatic relief of pain and inflammation. The patient was advised on supportive measures including leg elevation, compression stockings, and activity modification. Given the self-limiting nature of idiopathic erythema nodosum, no additional systemic therapy was deemed necessary at presentation.

Outcome and Follow-up

The patient was scheduled for follow-up in 4-6 weeks to monitor lesion resolution and assess for any new developments. She was counseled on the typical course of erythema nodosum, with most lesions resolving within 3-6 weeks without scarring. Instructions were provided to return immediately if systemic symptoms developed or if new lesions continued to appear beyond the expected timeframe.