Hồng ban nút (Erythema nodosum)

Mô tả: A skin disorder of acute-onset eruption of red, tender nodules and plaques predominantly over the lower extremities and, in particular, the extensor surfaces.

Nguyên nhân: More common31 • Inflammatory bowel disease • Infections • Sarcoidosis • Rheumatological disorders • Drug reactions – especially to sulfonamides and the oral contraceptive pill • Malignancies • Pregnancy

Cơ chế: The root cause is thought to be a hypersensitivity reaction to a variety of stimuli. The theory is that immune complexes form after exposure to an antigen and are deposited in venules around subcutaneous fat and connective tissue.31 The subsequent inflammation causes the characteristic lesions. A number of immunological • Reactive oxidative species have been found at lesion sites.32 • Delayed-type hypersensitivity histopathology has been found at mature lesion sites.33 • Complement activation has also been implicated.34 Why the lesions appear on the shins has not been explained. It has been suggested that a combination of a relatively meagre arterial supply, combined with a venous system that is subject to gravitational effects and has no mechanical pump and an inadequate lymphatic system favour deposition in that area.35

Ý nghĩa lâm sàng: Erythema nodosum is not a sensitive or specific sign. However, if found a review of the common causes is often completed. A recent study has found it to be present in approximately 4% of inflammatory bowel disorder patients.36