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This is a case of erythema nodosum (EN) secondary to Inflammatory Bowel Disease (IBD) . Almost 50% of cases of EN are idiopathic but can be associated with many other entities that are not necessarily limited to sarcoidosis and IBD. It is likely a delayed hypersensitivity reaction to various antigens resulting in tender nodular inflammation of subcutaneous adipose tissue usually on the shins.
Erythema Nodosum due to IBD