Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Erythema nodosum, idiopathic ?
    ### Response:
    Erythema nodosum (EN) is a skin condition in which red bumps (nodules) form on the shins. Less commonly, the nodules form on other areas of the body such as the thighs and forearms. The lesions begin as firm, hot, red, painful lumps and progress to a purplish color.
    