Erythema Multiforme Overview

Erythema Multiforme

• Cause: A reaction to infection (90% of cases), often herpes simplex, or a drug (50% of cases). Sometimes no provoking factor is found.
• Presentation: Upper respiratory infection symptoms may precede the eruption. Annular, non-scaling plaques appear mainly on extremities (palms, soles, forearms, legs). Individual lesions get bigger but clear in the center, creating a target appearance. Mucous membrane involvement (oral, genital, ocular, pharyngeal) occurs in more severe (major) cases, often with fever and malaise. Some lesions may blister.
• Course: New lesions appear over 1-2 weeks, until the provoking factor is gone. Individual lesions last a few days. Grey or brown patches mark the site of resolved lesions. Recurring bouts of lesions (with repeated attacks) are possible and may last years. Herpes simplex infection is often a trigger.
• Complications: Usually no complications. Severe lesions in the respiratory tract can lead to asphyxia. Eye ulcers can cause blindness. Genital ulcers can cause urinary retention and phimosis or vaginal stricture.

Stevens-Johnson Syndrome

• Relationship to Erythema Multiforme: No longer considered a severe form of erythema multiforme; it's now considered part of the toxic epidermal necrolysis (TEN) spectrum of diseases.

Erythema Nodosum

• Definition: Inflammation of subcutaneous fat (panniculitis). Specifically septal panniculitis, with inflammation confined to the septae between fat lobules.
• Presentation: Tender red nodules (alone or in groups) appear mostly on the legs and forearms, sometimes on thighs, face, breasts, or other fatty areas. Some patients experience painful joints and fever.
• Course: Individual lesions resolve over 2 weeks. New lesions can arise over a period of 6-8 weeks. Persistent lesions may be called nodular vasculitis.
• Complications: Nodules can be very painful, making walking difficult. Erythema nodosum leprosum can occur in leprosy patients with established cell-mediated immunity against Mycobacterium leprae, resulting in serious illness (severe malaise, arthralgia, and fever).

Vasculitis

• Definition: Inflammation of blood vessel walls, characterized by endothelial cell swelling, necrosis, or fibrinoid change. Clinical presentation can vary based on the size of the affected vessel.
• Causes: Immune complexes lodge in vessel walls (primarily postcapillary venules) activating complement, drawing in neutrophils that damage the vessel wall. Common antigens include drugs, autoantigens and infectious agents.
• Presentation: Painful palpable purpura is common (in dependent areas like the legs and forearms in ambulatory patients. Buttocks and flanks in bedridden ones) The lesions might have a dark center (necrosis). Henoch-Schönlein purpura, a type of vasculitis is common in children, often following a respiratory tract infection. Urticarial vasculitis is also possible, presenting as burning, raised lesions lasting >24 hours, potentially with purpuric foci in the wheals.
• Course: Course varies depending on the cause, affected vessel size, extent of involvement, and organ involvement. Some types spontaneously resolve; others can be chronic or recurrent.
• Complications: Vasculitis can affect many organs (kidneys, CNS, GI tract, lungs).

Wegener's Granulomatosis

• Cause: Granulomatous vasculitis of unknown cause.
• Presentation: Fever, weight loss, fatigue, nasorespiratory symptoms (rhinitis, hearing loss), and often symmetrical skin lesions (ulcers or papules). Internal organs (eyes, joints, heart, nerves, lungs, and kidneys) can be involved.
• Typical features: Antineutrophil antibodies (usually C-ANCA with anti-PR3 specificity).
• Treatment: Cyclophosphamide is the treatment of choice, often used together with steroids.

Polyarteritis Nodosa

• Cause: Necrotizing vasculitis affecting medium-sized vessels; the cause is often unknown or related to immune complexes, sometimes containing hepatitis B or C, or linked to certain antigens, B-cell lymphomas, and other immunotherapies.
• Presentation: Tender subcutaneous nodules along arteries, potentially ulcerating or becoming necrotic.
• Clinical Manifestations: May be systemic, involving kidneys, gut, heart, nerves, testicles, and joints. Cutaneous involvement is possible. Symptoms can include fever, weight loss, pain in muscles or joints, and abdominal pain. Renal involvement is common.