Erythema nodosum in renal transplant recipients: multiple cases and review of literature.

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 multinucleated giant cells are the main findings in late stage. Etiological management - by anti-tuberculous therapy in Cases 1 and 2, by salazopyrin in Case 3, and by discontinuation of ciprofloxacin in Case 4 - was associated with regression. Erythema nodosum can develop in renal transplant patients who did not receive induction therapy, non-rejecters, and those with steroid-free protocols. Management of erythema nodosum should be directed to the underlying associated condition, which could be tuberculosis, inflammatory bowel disease, or drug related.