A 13 year old girl presented with a 4 day history of general malaise, painful knees and ankles and a 1 day history of a rash isolated to the anterior aspect of both lower legs. The rash started as shiny, tender nodules that gradually coalesced. The girl had no previous medical history and was not taking any medication.
The painful rash.
Q1. What is this rash called?
Q2. What are the possible causes?
Erythema nodosum.
Idiopathic, infection (such as post-streptococcal, TB, mycoplasma), systemic diease (such as inflammatory bowel disease, sarcoidosis, malignancy) and drugs (such as sulfonamides, oral contraceptives).
Erythema nodosum (EN) is the most common form of panniculitis (inflammation of subcutaenous fat). It typically presents with smooth, red nodules that are painful. The nodules may coalesce. Most commonly EN occurs on the anterior surface of the lower legs but may occur is other locations such as the thighs and forearms (Mana, Marcoval. Erythema nodosum. Clinics in Dermatology. 2007;25(3):288-294).
