Dermatology Lecture 12 PDF 2022-2023

# Dermatology ## Lecture 12: Erythema Multiforme & Nodosum & Drug Reactions & Epidermal Necrolysis & Pemphigus Vulgaris ### 2022-2023 ## Erythema Multiforme (EM) ### Definition: Acute self-limited skin disease characterized by target or iris lesion. ### Etiology: Immune mediated common reaction...

# Dermatology ## Lecture 12: Erythema Multiforme & Nodosum & Drug Reactions & Epidermal Necrolysis & Pemphigus Vulgaris ### 2022-2023 ## Erythema Multiforme (EM) ### Definition: Acute self-limited skin disease characterized by target or iris lesion. ### Etiology: Immune mediated common reaction pattern to various antigenic stimuli such as: - **Infections:** - **Viral:** herpes simplex (The most common precipitating factor). - **Mycoplasma infection.** - **Drugs** - **Idiopathic** EM has two subtypes: EM minor & EM major. ### EM minor: - **Prodroma:** is absent or mild. - **Skin lesions:** without mucous membrane involvement. - **Skin lesions:** - **Distribution:** Bilateral & symmetrical distribution on the extensor surface of extremities (hands, feet, forearm). Face, neck and trunk are less commonly affected. - **Shape:** Polymorphic. - The most characteristic is the target or irish lesion. The classic “target” or “iris” lesion is circular with three zones (alternating dark and light): - **Central:** cyanotic or purpuric, Vesicle or bulla may occur in the centre - **Pale Ring** - **Periphery:** erythematous & Edematous area surrounding the pale ring - Asymptomatic but there may be itching or burning sensation. ### EM major: - **Skin lesions:** with involvement of mucous membrane - **Systemic symptoms:** are always present (Fever, occasionally arthralgia (constitutional ++ve) or pneumonia) - **Skin lesions:** as EM minor or severe wide-spread Vesiculo-bullous eruption - **Mucous membrane lesions:** - Oral: erosions, vesicles and bullae - Lips: haemorrhagic crusts - Eyes: conjunctivitis, corneal ulcer - Nasal - uretheral and anal mucosa may be inflammed and eroded ## Erythema Nodosum ### Definition: Inflammation of subcutaneous fat (panniculitis) presents as an acute self-limited painful nodular erythematous eruption. It is an allergic reaction to: - **Infections:** - **Bacteria:** streptococci - **Viruses:** hepatitis, infectious mononucleosis, upper respiratory tract infection - **Mycobacteria:** leprosy.. - **Drugs:** sulfa, contraceptive pill.. - **Others:** Sarcoidosis, malignancy, (enteropathies) IBD - **Idiopathic:** 30-50% ### Clinical Picture: - **Prodroma:** URT infections - **General:** fever, malaise, arthritis, or arthralgia - **Skin lesion:** - Painful tender. Bilateral. Shiny red nodules - Healing: Bruise colour changes. - Site: Chin of tibia (commonest), occasionally forearm and thigh - Show bruise-like colour changes during regression. ## Drug Reactions ### Definition: Drug reaction is harmful, unintended response to drug in the therapeutic dose. ### Mechanism: Allergic or non-allergic ### Clinical Picture: The important forms of the drug eruptions include: #### Severe life-threatening drug reactions: - **Anaphylactic shock:** pallor, hypotension, bronchospasm, angioedema - **Erythroderma** - **Epidermal necrolysis:** Stevens-Johnson Syndrome & Toxic epidermal necrolysis (TEN)*Page 7* - **Drug reaction with eosinophilia and systemic symptoms (DRESS):** skin rash, facial oedema, eosinophilia, lymphadenopathy and organ affection (liver, kidney,..) ## Other forms of drug reaction: - **Urticaria (Penicillin, aspirin)** - **Exanthematous rash:** Red maculopapular rash (like measles) - **Photosensitivity (Psoralen, Tetracycline).** - **Vascular eruption or purpuric lesion** - **Lichenoid eruption** - **Bullous eruption** - **Acne-form eruption:** inflammatory papules or pustules that have a follicular pattern (corticosteroids, ACTH, Bromide, Iodide, Isoniazide) - **Pigmentation:** antimalarial, phenothiazine, gold - **Alopecia (following chemotherapy)** - **Fixed drug eruption:** It characteristically recurs in the same sites each time the drug is administered. Common drugs causing fixed eruption are: Sulfonamides, NSAIDs - **Clinical picture:** Well-defined round or oval plaque of erythema & oedema. Bulla may develop on the top. - **Healed lesion:** is hyperpigmented (dark brown to violet). - **Common sites involved:** are: lips, anogenital area (glans penis), but can occur anywhere. ## Diagnosis of drug reactions: - **Abrupt onset symmetric cutaneous eruption** - **History of drug intake.** - **De-challenge test:** The eruption improves when the suspected drug is stopped. (clear in 2 weeks on withdrawal) - **Re-challenge (oral provocation test))** ## Treatment of drug reactions: - **Elimination of the offending drug** - **Symptomatic treatment:** - **Antihistamines.** - **Topical steroid.** - **Systemic steroids in severe cases.** ## Epidermal Necrolysis ### Definition: (Stevens-Johnson Syndrome & Toxic epidermal necrolysis) Acute, drug induced, life-threatening mucocutaneous reactions. Characterized by extensive necrosis and detachment of the epidermis. - **Stevens-Johnson Syndrome (SJS):** less than 10% - **SJS-TEN overlaps:** 10-30% - **Toxic epidermal necrolysis (TEN):** more than 30% ### Prodome: - High fever, painful skin and weakness. ### Clinical features: - **Skin:** Erythematous and purpuric macules on trunk and proximal limbs → flaccid blisters → epidermal detachment and large confluent oozing erosions. - **Nikolsky sign:** is positive (firm sliding pressure on normal appearing skin → detachment of intact superficial epidermis). - **Sites:** mainly localized to face,upper trunk, and hands - **Mucous membrane:** - Involvement in 90% of cases (always at least two sites) - Erythema and painful erosions of buccal, ocular, and genital mucosa - **Visceral involvement:** is possible (pulmonary, GIT, renal) ### Prognosis: - **Mortality rate:** is up 25%. - **Death:** may be due to sepsis, electrolyte imbalance or organ failure. ### Ttt: - **Early (immediate) withdrawal of suspected drugs.** - **Rapid initiation of supportive care in intensive care burn unit.** ## Pemphigus vulgaris ### Definition: Autoimmune disease in which autoantibodies are formed against intercellular bridges of the prickle cell layer. This results in acantholysis and formation of intraepidermal bullae. ### Incidence: Rare chronic disease, usually affects adults. (4-5th decades) - **Lesion:** Characterized by flaccid bullae arising upon normal skin and mucous membranes. The bullae rupture easily leaving painful erosions & crusts. - **Painful erosions:** on mucous membrane. - **Complication:** Infection, fluid & electrolyte imbalance may result in death. - **Nikolsky sign:** is positive ### Clinical picture: - **Sites:** commonly involved are scalp, intertriginous area and umbilicus, but in severe cases any site can be involved. ### Treatment: - **Refer to dermatologist** - **Systemic steroids & immunosuppressive (cytotoxic) drugs.** ## Case scenario ### Case 1 scenario - Mona is a 40-year-old lady with erythematous asymptomatic skin lesions on hands and feet of two weeks duration. - One week before the appearance of these lesions she had common cold and developed sores and crusts on lips - **Skin exam:** MONA was diagnosed to have erythema multiforme after herpes simplex infection ### Case 2 scenario - Ola is a 29-year- old lady presented to emergency room with a painful,expanding and sloughing rash. She was recently diagnosed to have a urinary tract infection, on treatment with Bactr. - **Skin examination:** Erythematous erosions, mainly localized on the face, upper trunk and hands. - **Lesions:** began as flaccid blisters ## Answer: Ola was diagnosed to have severe drug reaction of Epidermal Necrolysis spectrum. This spectrum includes Stevens Johnson Syndrome and toxic epidermal necrolysis. # Questions 1. What is the characteristic lesion of erythema multiform? **A: target lesion** 2. What is the characterestic lesion of erythema nodosum? **A: nodules** 3. Mention two life threatening drug reactions **A: DRESS and TEN Spectrum** 4. What is the primary lesion of pemphigus vulgaris? **A: Flacid bullae** 5. What is the difference between a vesicle and a bulla? **A: Depth (distinguishes erosion and ulcer)** ## Questions 58 1- bullae are expected finding in: **E: pemphigus** 2- Target lesion occurs in: **C: Erythema multiforme** 3- Erythema multiforme is characterized by: **B: Could be precipitated by herpes simplex infection**