Erythema nodosum

Pre-eruptive phase The first signs of erythema nodosum are often flu-like symptoms such as a fever, cough, malaise, and aching joints. Some people also experience stiffness or swelling in the joints and weight loss. Eruptive phase Erythema nodosum is characterised by nodules (rounded lumps) below the skin surface, usually on the shins. These subcutaneous nodules can appear anywhere on the body, but the most common sites are the shins, arms, thighs, and torso. Each nodule typically disappears after around two weeks, though new ones may continue to form for up to six or eight weeks. Joint pain and inflammation sometimes continue for several weeks or months after the nodules appear. Less common variants of erythema nodosum include: • Ulcerating forms, seen in Crohn's disease • Erythema contusiforme, when a subcutaneous hemorrhage (bleeding under the skin) occurs with an erythema nodosum lesion, causing the lesion to look like a contusion (bruise) • Erythema nodosum migrans (also known as subacute nodular migratory panniculitis), a rare form of chronic erythema nodosum characterized by asymmetrical nodules that are mildly tender and migrate over time. File:EN-TBC.PNG|Erythema nodosum lesion in a person with light skin and tuberculosis File:A single EN.JPG|A single lesion of erythema nodosum File:Erythema Nodosum.jpg|Several lesions of erythema nodosum in an individual with dark skin ==Causes==

EN is associated with a wide variety of conditions. Idiopathic About 30–50% of EN cases are idiopathic (of an unknown cause). Infection Infections associated with EN include: leprosy, and M. avium complex • Mycoplasma pneumoniae • Histoplasma capsulatum • Yersinia • Lymphogranuloma venereum (LGV), caused by the bacteria Chlamydia trachomatis • Epstein-Barr virus • Coccidioides immitis (Valley fever) • Cat scratch disease Autoimmune Autoimmune disorders associated with EN include: • Sarcoidosis Pregnancy Pregnancy may be associated with EN. • Omeprazole • Sulfonamides • Oral contraceptives • Penicillins • Bromides • Hepatitis B vaccination Cancer Cancers associated with EN include: There is an association with the HLA-B27 histocompatibility antigen, which is present in 65% of patients with erythema nodosum. A useful mnemonic for causes is SORE SHINS (Streptococci, OCP, Rickettsia, Eponymous (Behçet), Sulfonamides, Hansen's Disease (Leprosy), IBD, NHL, Sarcoidosis. ==Pathophysiology==

Erythema nodosum is probably a delayed hypersensitivity reaction to a variety of antigens. Although circulating immune complexes have been demonstrated in patients with inflammatory bowel disease, they have not been found in idiopathic or uncomplicated cases. ==Diagnosis==

Erythema nodosum is diagnosed clinically. A biopsy can be taken and examined microscopically to confirm an uncertain diagnosis. The ESR is typically high, the C-reactive protein elevated, and the blood showing an increase in white blood cells. The ESR is initially very high and falls as the nodules of erythema nodosum. The ASO titer is high in cases associated with a streptococcal throat infection. A chest X-ray should be performed to rule out pulmonary diseases, in particular sarcoidosis and Löfgren syndrome. ==Treatment==

Erythema nodosum is self-limiting and usually resolves within 3–6 weeks. A recurring form does exist, and in children, it is attributed to repeated infections with streptococcus. Thalidomide has been used successfully in the treatment of Erythema nodosum leprosum, and it was approved by the U.S. FDA for this use in July 1998. According to a 2009 meta-analysis, there is some evidence of benefit for both thalidomide and clofazimine in the treatment of erythema nodosum leprosum. ==Epidemiology==

Erythema nodosum is the most common form of panniculitis. It is most common in the ages of 20–30, and affects women 3–6 times more than men. ==Eponym==

The term, Subacute Migratory Panniculitis of Vilanova and Piñol, was named after the two Catalan dermatologists who provided a brief description and explanation of the disease, Xavier Montiu Vilanova (1902–1965) and Joaquin Aguade Piñol (1918–1977), in 1954, and was named in 1956. ==References==