Overview

Erythema nodosum is an inflammatory condition characterized by the sudden appearance of tender, red bumps or nodules, usually located on the front of the lower legs. It is considered a type of panniculitis, meaning inflammation of the fat layer under the skin. Erythema nodosum is not a disease by itself but rather a reaction to various underlying conditions, including infections, autoimmune diseases, and certain medications. While the condition can be uncomfortable and sometimes painful, it usually resolves on its own within a few weeks without leaving permanent scars.

Causes

Erythema nodosum can be triggered by a variety of factors, and in some cases, the exact cause remains unknown. Common causes include:

• Infections: Streptococcal throat infections, tuberculosis, fungal infections, and other bacterial or viral illnesses.
• Autoimmune Diseases: Conditions like sarcoidosis, inflammatory bowel disease (Crohn’s disease, ulcerative colitis), and Behçet's disease.
• Medications: Certain medications such as oral contraceptives, sulfonamides, and antibiotics like penicillin can provoke a reaction.
• Pregnancy: Hormonal changes during pregnancy can contribute to the development of erythema nodosum.
• Cancers: Though rare, underlying malignancies such as lymphoma or leukemia may be associated with this condition.
• Idiopathic: In many cases, no specific cause is identified, especially in otherwise healthy individuals.

Symptoms

The primary symptoms of erythema nodosum are related to skin changes, but systemic symptoms can also occur:

• Tender Red Nodules: Painful, red, raised bumps typically found on the shins, but can also appear on thighs, forearms, or other areas.
• Skin Color Changes: The nodules may change color like a bruise (from red to purple to brown) as they heal.
• Fever: Mild fever may accompany the skin symptoms.
• Fatigue: General tiredness or weakness is common in more severe cases.
• Joint Pain: Swelling and pain in joints, especially the knees and ankles, may occur alongside the skin lesions.
• No Scarring: The nodules usually resolve without scarring, although slight skin discoloration may persist temporarily.

Diagnosis

Diagnosis of erythema nodosum is typically based on clinical evaluation and supportive testing:

• Medical History: Reviewing recent infections, medication use, and any chronic illnesses.
• Physical Examination: Identifying characteristic nodules, their location, and appearance.
• Blood Tests: Checking for signs of infection, inflammation markers (like ESR and CRP), and autoimmune indicators.
• Throat Culture: To detect streptococcal infection if recent sore throat is reported.
• Chest X-ray: Performed to check for sarcoidosis or tuberculosis in certain cases.
• Skin Biopsy: Rarely needed but can confirm diagnosis by showing inflammation in the fat layer under the skin.

Treatment

Treatment focuses on addressing the underlying cause and relieving symptoms:

• Rest and Leg Elevation: Reducing physical activity and elevating the legs can ease discomfort.
• Anti-inflammatory Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen help relieve pain and swelling.
• Corticosteroids: In more severe cases, oral or topical steroids may be prescribed to reduce inflammation.
• Treating Underlying Condition: If a specific infection or disease is identified, appropriate treatment (antibiotics, antitubercular therapy, etc.) is given.
• Cold Compresses: Applying cold packs to affected areas can help reduce pain and inflammation.
• Compression Stockings: Sometimes recommended to manage leg swelling and improve comfort.

Prognosis

The overall prognosis for erythema nodosum is favorable:

• Self-Limiting Course: Most cases resolve within 3 to 6 weeks, even without treatment.
• No Permanent Skin Damage: Skin usually heals without scarring, though some pigmentation changes may temporarily persist.
• Low Recurrence Rate: Some individuals may experience recurrent episodes, especially if the underlying cause is chronic or untreated.
• Good Outcome with Treatment: Identifying and treating the cause ensures quicker resolution and prevents recurrence.
• Minimal Long-Term Impact: For most individuals, erythema nodosum is a transient condition with an excellent long-term outlook.

With appropriate care and management of underlying factors, people with erythema nodosum typically recover fully and return to normal activities.