erythema nodosum

painful red nodules usually over both shins (but may occur elsewhere) due to a hypersensitivity inflammatory reactions of the subcutaneous fat cells (panniculitis)

often associated with fever, malaise, and joint pain

nodules usually subside over a period of 2–6 weeks without ulceration or scarring

diagnosis is clinical but patients are usually investigated to exclude important causal precipitant conditions

an association with the HLA-B27 histocompatibility antigen, which is present in 65% of patients with erythema nodosum

peak incidence between 18–36 years of age

women are 3-6 times more affected than men

30-50% are idiopathic

pregnancy

medications - combined oral contraceptive pill (OCP), sulphonamides

vaccinations

Behçet's disease

lepromatous leprosy

these should be targetted according to likely precipitants

FBE, ESR, ASOT, throat swab, urinalysis

CXR - hilar LNs may be due to TB, sarcoidosis or Löfgren syndrome (a form of acute sarcoidosis with erythema nodosum, bilateral hilar adenopathy, fever, and often accompanied by joint symptoms).

consider TB screen

Rx any streptococcal infection or other underlying cause

bed rest, elevation of legs, compressive bandages

non-steroidal anti-inflammatory drugs (NSAIDs) are more useful in acute forms

Corticosteroids and colchicine can be used in severe refractory cases