What is Erythema Nodosum?
Erythema nodosum (EN) is an inflammatory condition characterized by the presence of tender, red nodules or lumps, usually on the shins. It is often a hypersensitivity reaction to a variety of stimuli, including infections, medications, and other inflammatory disorders.
Histological Features
Histologically, erythema nodosum is classified as a
panniculitis, which is an inflammation of the subcutaneous fat. The hallmark of EN is the presence of septal panniculitis without vasculitis. Key histological features include:
Septal thickening: Inflammation primarily occurs in the septa of the subcutaneous tissue.
Mixed inflammatory infiltrate: The infiltrate is composed of lymphocytes, histiocytes, multinucleated giant cells, and occasionally neutrophils.
Miescher's radial granulomas: These are small, well-formed granulomas typically found around the blood vessels in the septa.
Absence of vasculitis: Unlike other forms of panniculitis, EN lacks vascular inflammation.
Infections: Streptococcal infections are the most common cause. Others include tuberculosis, Yersinia, and mycoplasma.
Medications: Drugs such as sulfonamides, oral contraceptives, and certain antibiotics can induce EN.
Autoimmune diseases: Conditions like sarcoidosis, inflammatory bowel disease, and Behçet's disease are associated with EN.
Clinical Presentation
Patients with erythema nodosum typically present with: Red, tender nodules: These are usually located on the anterior aspects of the legs.
Systemic symptoms: Fever, malaise, and joint pain may accompany the skin lesions.
Self-limiting course: EN often resolves spontaneously within 3 to 6 weeks.
Diagnosis
The diagnosis of erythema nodosum is primarily clinical, supported by histological examination. A
skin biopsy can confirm the diagnosis by revealing the characteristic histological features. Additional investigations may be warranted to identify underlying causes.
Treatment
Treatment of erythema nodosum involves addressing the underlying cause and symptomatic relief. Common approaches include: NSAIDs: Nonsteroidal anti-inflammatory drugs can help alleviate pain and inflammation.
Corticosteroids: In severe cases, corticosteroids may be prescribed to reduce inflammation.
Treating underlying conditions: Identifying and managing the root cause is crucial for effective treatment.
Prognosis
The prognosis for erythema nodosum is generally good, as it is often a self-limiting condition. However, recurrence is possible, especially if the underlying cause is not addressed. Continuous monitoring and management of associated conditions are essential to prevent relapses.
