We report 4 renal transplant recipients with erythema nodosum. Erythema nodosum is a cutaneous inflammatory reaction located on the anterior aspects of the lower extremities. It may be associated with a wide variety of diseases, including infections (as in Cases 1 and 2), sarcoidosis, rheumatologic diseases, inflammatory bowel diseases (as in Case 3), medications (as in Case 4), autoimmune disorders, pregnancy, and malignancies. Histopathologically, erythema nodosum is the stereotypical example of a mostly septal panniculitis with no vasculitis, and the inflammatory infiltrate in the septa varies with age of the lesion. In early lesions edema, hemorrhage, and neutrophils are responsible for the septal thickening, whereas fibrosis, peri-septal granulation tissue, lymphocytes, and multinucle… Source: MedWorm: Sarcoidosis