Erythema Nodosum

Erythema nodosum consists of raised, red, warm, painful swellings the size of a hazelnut or walnut (usually 2-6 cm in diameter) that develop suddenly (acutely) in the skin on the front of the legs, usually at and below the knee, and on the feet. When they appear close to a joint, they can sometimes be confused with arthritis. Rarely, there is also a chronic and frequently recurring form. Erythema nodosum is a condition in which the skin over-reacts. It is a sterile inflammation of the fat tissue under the skin. It is very painful. It causes flu-like complaints such as fever, generalised body aches, joint pain and weakness. These painful red swellings never come to a head; this is how they differ from spots, abscesses, carbuncles or furuncles (carbuncles and furuncles are bacterial infections under the skin). Whatever the cause, the pathology is always a septal panniculitis (inflammation of the fat tissue). Only in erythema nodosum occurring in patients with Behçet's disease may there also be signs of inflammation of the vessel walls (vasculitis = perivascular infiltration). It usually clears without leaving a mark; lesions due to Behçet's disease can leave dark marks on the skin. For this reason, taking a biopsy from a patient with erythema nodosum for a pathological diagnosis is a largely unnecessary procedure. Erythema nodosum due to infection usually heals within 7 weeks even without treatment, but can sometimes last 5-6 months.

Erythema nodosum has many causes, but the most common is a throat infection caused by streptococci.

• Bacterial infections: It most often develops after a streptococcal throat infection. Others include tuberculosis, Yersinia enterocolitis (a Gram-negative bacillus causing diarrhoea and abdominal pain), Mycoplasma pneumoniae infection, lymphogranuloma venereum, and Campylobacter and Salmonella infections.
• Sarcoidosis: Erythema nodosum develops in 22% of patients. In acute sarcoidosis, the combination of erythema nodosum, fever, arthritis and uveitis is also called Löfgren's syndrome.
• Behçet's disease: Erythema nodosum is one of the diagnostic criteria for Behçet's disease.
• Fungal infections: Such as coccidioidomycosis, histoplasmosis and blastomycosis.
• Medicines: Such as sulphonamides, sulphonylureas and oral contraceptives.
• Inflammatory bowel diseases: Ulcerative colitis, erythema nodosum,
• Pregnancy: In some patients it may appear in the second three months (trimester) of pregnancy.
• Hodgkin's disease and lymphoma
• Some vasculitides, such as temporal arteritis.

Laboratory tests for streptococcal infection: throat culture, a rapid streptococcal screening test or ASO (anti-streptolysin O: shows a past streptococcal infection). Stool culture or antigen screening tests: investigation for Salmonella, Yersinia and Campylobacter. A chest X-ray can be taken to screen for widening of the hilar region, i.e. sarcoidosis with lymphadenopathy in that area. For sarcoidosis, the ACE (angiotensin-converting enzyme) level in the blood can also be checked. Causes such as inflammatory bowel disease, Behçet's disease and medicines are all diagnoses based on a detailed history and examination.

Treatment:

In most patients it heals quickly with non-steroidal anti-inflammatory (non-cortisone) medicines, cold applications, elevation of the legs and rest. In cases resistant to treatment, steroids can be used for a short time. Colchicine treatment is used, particularly in Behçet's disease or in frequently recurring erythema nodosum. Very rarely, under the follow-up of a rheumatologist, potassium iodide and certain rheumatological medicines may also be used.

Panniculitis

Panniculitis is known as a type of inflammatory reaction of the fat tissue under the skin. Although the disease has many different types, its appearance is almost the same in all of them. The diagnosis is made by skin biopsy. The types of panniculitis are difficult to classify, and classification is usually based on the part of the fat tissue involved.

What does the disease look like clinically?

The affected area of skin is thickened. There may or may not be a change in skin colour; the skin may be red or brownish. These areas are often tender. The affected areas are often raised above the skin as swellings beneath it, but sometimes the findings may spread over large areas. When the disease regresses, permanent or temporary dimples may remain in the skin.

How is it treated?

• Causes that may trigger the disease, such as medication use or infection, should be removed.
• The affected area should be kept elevated and rested.
• If tolerated, stockings applying 18-25 mm Hg of pressure to the legs can be used.
• Anti-inflammatory medicines such as aspirin, ibuprofen or diclofenac can be used.
• Corticosteroid treatment by mouth or by injection can be given.
• Anti-inflammatory medicines such as tetracycline or hydroxychloroquine are used.
• Surgery can be performed when lesions do not heal and turn into ulcers.