بسم الله الرحمن الرحيم

DRUG REACTIONS ERYTHEMA MULTIFORME ERYTHEMA NODOSUM

DRUG REACTIONS

Definition: Cutaneous eruptions caused by drugs. Incidence: Common in outpatient practice. Common cause of dermatological consultation in hospital inpatient wards.

Mechanism: 1) Immunologically mediated: Hypersensitivity reaction (Drug allergy) Type 1 (Ig E mediated). Type 2 (Antibody dependant cellular cytotoxicity). Type 3 (Immune complex mediated). Type 4 (Delayed type hypersensitivity reaction). 2) Non-immunologically mediated: Abnormal drug metabolism.

Clinical forms frequently encountered: 1)Erythemas: morbilliform erythema, erythema multiforme, erythema nodosum. 2)TEN. 3)Fixed drug eruption. 4)Urticaria and angioeodema. 5)Photosensitive drug reactions. 6)Acneform eruptions. 7)Lichenoid eruptions. 8)Skin necrosis. 9)Pigmentations. 10)Erythroderma (Exfoliative dermatitis).

Common causative drugs: Sulfa preparations. Aspirin. NSAIDs. Antibiotics. Contaceptive Pills. Psychotropic drugs. Cytotoxic drugs. Anti-convulsants.

ERYTHEMA MULTIFORME

Definition: Acute eruption of the skin +/- mucous membranes. Erythema multiforme minor: Skin only. No or mild mucous affection. Erythema multiforme major (Stevens Johnson syndrome) Wide spread skin affection. Severe mucous membrane affection. Systemic affection. Mortality.

Etiopathogenesis: Precisely unknown. Immunologically mediated. Activated T-cells (Cytokines / Cytotoxic T-cells). Triggering factors: 1)Infections: Herpes simplex (HAEM) / Mycobacteria. 2)Drugs. 3)Collagen diseases: SLE. 4)Internal malignancy. 5)Pregnancy. 6)Radiotherapy. 7)50% idiopathic.

C/P: TARGET LESION Sharply defined red macule Edematous papule Iris (Target) lesion 1)Dusky red center +/- vesicles and bullae (Herpes iris). 2)Edematous pale rim. 3)Peripheral erythema.

Erythema multiforme minor: Bilateral and symmetrical. Acral parts. Rare face affection. May be painful or pruritic. No or mild mucosal involvement (only oral mucosa).

Erythema multiforme major: Widespread skin affection. Starts mainly on trunk  Spreads. Coalescent erythematous patches (Atypical target lesions). Prominent vesicles and bullae (Nikolsky’s sign). Painful and tender. Severe mucous membrane affection: Oral, Nasal, ocular, Pharyngeal, Genital. Flaccid blisters, erosions and crustations. Systemic affection: Fever, malaise and myalgia. Pneumonia, sepsis, acute tubular necrosis. DEATH.

Treatment: Identification and management of possible triggering factors. Erythema multiforme minor: 1)Topical steroids. 2)Soothing preparations. 3)Antihistaminics.

Erythema multiforme major: 1)Hospitalization. 2)Antibiotics. 3)IV fluids. 4)Topical wet compresses. 5)Oral antiseptics. 6)Eye care. 7)Systemic steroids. 8)Antihistaminics / Analgesics. 9)Management of systemic complications.

ERYTHEMA NODOSUM

Etiological factors: Infections: Beta haemolytic streptococci. TB. Leprosy (ENL). Intestinal infections (Yersinia / Shigella / Salmonella). Systemic fungal infections. Drugs: Contraceptives, iodides, bromides, sulfonamides. Sarcoidosis. Inflammatory bowel diseases: Ulcerative colitis / Chron’s disease.

C/P: Age: years. Sex: Three times more common in females. Constitutional symptoms: Fever, malaise, myalgias, and arthralgias (often of ankles or knees).

Skin eruption: Multiple, bilateral but not necessarily symmetrical, discrete painful lesions, affecting the shins of lower legs; less frequently, the knees and arms are affected. The eruption lasts for about 6 weeks. Individual lesion: A deeply-seated tender nodule; oval, round or arciform elevation with ill-defined margins. Nodular character is better palpated than seen. Size ranges from 1 to 10 cm in diameter. Color is dusky (dull red)  Violaceous  Yellow-brown, resembling a resolving bruise. Blistering and ulceration do not occur and lesions resolve without scarring.

Treatment: Management of the cause. Bed rest and leg support. Analgesucs, aspirin, NSAIDs. Potassium iodide. Intralesional steroids. Systemic steroids: In severe cases.

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