Erythema Nodosum

Arthralgias with Painful Erythematous Nodules on Lower Legs

Patricia Reichert, DO, LT MC USN, and Michele Sprosty, MD, LCDR MC USN
Naval Hospital Jacksonville, Jacksonville, FL


A 20-year-old active duty female presented to the clinic with a 10-day history of bilateral symmetrical arthalgias of her knees and elbows, and a tender rash on her lower extremities. She was 3 months post-partum. She reported an upper respiratory infection 3 weeks prior and had started oral contraceptives 4 weeks prior to presentation. She denied any recent travel, tick bites, or sexual contact. 

Physical Examination

Exam revealed tender, palpable, erythematous nodules over bilateral extensor surfaces of her lower extremities. There was a mild effusion to bilateral knees and ankles. 

What’s Your Diagnosis?

A. Superficial thrombophlebitis. 

B. Erythema nodosum.

C. Erythema induratum.

D. Henoch-Schönlein purpura. 

E. Subcutaneous granuloma annulare.

(Answer and discussion on next page)

Answer: Erythema nodosum

Erythema nodosum (EN) is a panniculitis, inflammation of subcutaneous fat tissue, usually without vasculitis. Skin findings are palpable dusky red, firm nodules with indistinct edges, most commonly on the anterior surfaces of the legs, but can also appear on the thighs and upper extremities.1 The nodules generally flatten, appearing bruise-like, and resolve within 2 to 8 weeks without residual scarring. 


Ankle edema and leg pain are common. The onset is acute and frequently associated with malaise, leg edema, and arthralgias (ankles, knees, and wrists are the most common).2 Women are affected more than men (3:1 vs 6:1) and the condition is most common in individuals age 15 to 40.

skin lesions


Diagnosis is clinical; streptococcal infection is the most common etiology. Evaluation to determine the etiology or underlying systemic disease should include a complete blood count, erythrocyte sedimentation rate, serum creatinine, blood urea nitrogen, antistreptolysin O titer, chest x-ray (CXR) and purified protein derivative (PPD) test.3 Pulmonary or gastrointestinal symptoms should enhance clinical suspicion for systemic causes, such as tuberculosis, sarcoidosis, or inflammatory bowel disease; a CXR, PPD, and stool cultures should thus be obtained.4 

If diagnosis is in question, a deep, incisional biopsy is recommended.4 Pregnancy and oral contraceptives cause a minority of cases. 


Treatment is symptomatic, as the disease is self-limited, and includes compression stockings, elevation, and NSAIDs.3 Potassium iodine—400 mg/d to 900 mg/d for 1 month—is a safe and effective adjunct treatment.3 

Differential Diagnosis

Erythema induratum (EI, or Bazin’s disease), Answer C, is a bilateral nodular panniculitis similar to EN. However, unlike EN, lesions are generally less red and tender, favor the posterior legs, tend to recur, and may ulcerate.2 With suspicion for EI or EN, PPD testing should be initiated as mycobacterium tuberculosis may be found in 50% to 70% of cases of EI.2 Treatment should be directed towards the underlying cause. 

Superficial thrombophlebitis (Answer A) is characterized by a painful, erythematous, cord-like induration. Subcutaneous nodules and postinflammatory hyperpigmentation may be evident.2 Etiologies include inheritable hypercoagulable states, as well as secondary causes, such as malignancy, varicose veins, pregnancy, and oral contraceptives.2 Treatment is directed at the underlying cause, with consideration for underlying DVT requiring anticoagulation. Compression stockings offer symptomatic relief. 

Henoch-Schönlein purpura (Answer D) typically presents as mottled purpura on the extensor aspects of the lower extremities with associated arthalgias, abdominal pain, and renal disease. Adult cases do occur, however it is most common in children age 4 to 8 with a viral infection or strep pharyngitis as the triggering event.2 Cutaneous symptoms may lag behind systemic symptoms up to 2 weeks. Treatment is primarily supportive; steroids or intravenous immunoglobulin may be warranted for severe abdominal pain or significant renal disease. NSAIDS should be avoided.

Subcutaneous granuloma annulare (GA), Answer E, presents as multiple, skin-colored nodules, up to several centimeters in diameter and present on the lower legs, dorsum of the feet, and hands.2 GA lesions are generally asymptomatic, precipitated by a history of trauma, and more common in children.2 No treatment is necessary as lesions are self-limited, although intralesional steroids may hasten resolution.

Patricia Reichert, DO, LT MC USN, is a staff physician at the Family Medicine Homeport clinic at Marine Corps Air Station Cherry Point in North Carolina.

Michele Sprosty, MD, LCDR MC USN, is an attending physician at the Family Medicine Residency at Naval Hospital Jacksonville in Jacksonville, FL, as well as the department head of the Family Medicine Homeport clinic.


1.Dolberg OT, Schlaeffer F, Greene VW, et al. Skin Disease: Diagnosis and Treatment. 2nd ed. Philadelphia, PA:Elsevier; 2005. 

2.James WD, Berger TG, Elston DM. Andrews’ Diseases of the Skin. 11th ed. Philadelphia, PA: Elsevier; 2011. 

3.Du Vivier A. Atlas of Clinical Dermatology. 3rd ed. Philadelphia, PA: Elsevier; 2002.

4.Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75:695-700.