Erythema multiforme and drug eruption Notes
Osmosis High-Yield Notes
This Osmosis High-Yield Note provides an overview of Erythema multiforme and drug eruption essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Erythema multiforme and drug eruption:

NOTES NOTES ERYTHEMA MULTIFORME & DRUG ERUPTION GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES DIAGNOSIS ▪ Skin, mucous membrane conditions ▪ Associated with medication use/infection LAB RESULTS CAUSES OTHER DIAGNOSTICS ▪ Exact mechanism unclear, severe immune reaction against foreign antigen ▪ Skin biopsy ▪ Clinical history TREATMENT COMPLICATIONS ▪ Initial rash may → epidermal layer loss ▪ Identify/remove/treat offending agent/ infection SIGNS & SYMPTOMS ▪ Desquamating skin, mucous membrane rash ERYTHEMA MULTIFORME osms.it/erythema-multiforme PATHOLOGY & CAUSES ▪ Immune-mediated, acute, self-limiting skin condition ▪ Type IV hypersensitivity CAUSES ▪ Suspected deposition of primarily IgMbound immune complexes in superficial skin, oral mucous membranes Infection (most) ▪ Viral ▫ Herpes simplex primary cause 16 OSMOSIS.ORG ▪ Bacterial ▫ Hemolytic Streptococci, Legionella, Mycobacterium, Mycoplasma pneumoniae, Neisseria meningitidis, Pneumococcus, Salmonella, Staphylococcus ▪ Parasitic ▫ Trichomonas, Toxoplasma gondii Drugs (rarely) ▪ Non-steroidal anti-inflammatories (NSAIDs), sulfonamides, phenytoin, barbiturates, phenylbutazone, penicillin, allopurinol

Chapter 3 Erythema Multiforme & Drug Eruption Physical factors ▪ Sunlight, radiotherapy, cold Autoimmune disease ▪ Vasculitides Hematological malignancy ▪ Non-Hodgkin lymphoma, leukemia, myeloid metaplasia RISK FACTORS ▪ < 20 years old ▪ ↑ frequency in biological males SIGNS & SYMPTOMS ▪ “Multiforme” denotes wide associated lesion variety ▪ Target lesions ▫ Initially round erythematous papules → dusky central area/blister, surrounded by dark red inflammation, surrounded by pale edematous ring, erythematous region on periphery ▪ Pruritus in affected area ▪ Painful lesions ▪ If severe ▫ Fever, weakness, malaise Erythema multiforme minor ▪ Often herpes simplex ▪ Involves skin (little/no mucous membrane involvement) ▪ Favors skin of extremities, face ▪ Symmetrical circular lesions ▪ Lesions become classic “target” lesions (red border, small white center) ▪ Rash spreads towards body center Erythema multiforme major ▪ Often drug-related ▪ Epidermal detachment/skin loss progression ▪ Erythematous, confluent, bullous lesions ▪ Involves mucous membranes ▪ Nikolsky’s sign (lightly rub skin with firm object for few seconds → blister forms) DIAGNOSIS LAB RESULTS ▪ Biopsy to exclude other skin disorders OTHER DIAGNOSTICS ▪ Identify offending agent/infection ▫ Identification: target lesions, symmetrical distribution TREATMENT ▪ Often self-resolving in 1–2 weeks MEDICATIONS ▪ Control primary cause ▫ Treat/remove identifiable causes ▫ Herpes simplex suspected: oral acyclovir/valaciclovir/famciclovir ▫ Eliminate possible offending drugs Figure 3.1 The abdomen of a child displaying numerous target lesions in a case of erythema multiforme. Mild disease ▪ Topical corticosteroids ▪ Antihistamines Severe Disease ▪ Glucocorticoids ▪ In severe cases, prednisone considered OSMOSIS.ORG 17

Recurrent disease ▪ Systemic antivirals (up to 6 months) ▪ Immunosuppression if antivirals fail STEVENS–JOHNSON SYNDROME & TOXIC EPIDERMAL NECROLYSIS osms.it/stevens-johnson_syndrome osms.it/toxic-epidermal-necrolysis PATHOLOGY & CAUSES ▪ Same underlying pathology (severity spectrum) ▫ Stevens–Johnson syndrome (lower end), toxic epidermal necrolysis (upper end) ▪ Severity, classification ▫ Body surface involvement % ▪ Severe mucocutaneous reaction → epidermal detachment COMPLICATIONS ▪ Dehydration, sepsis, pneumonia, multiple organ failure, renal tubular necrosis, acute renal failure, phimosis, vaginal synechiae (adhesions), inside eyelid-tissue scarring → corneal vascularisation → vision loss CAUSES ▪ Cytotoxic T cell mediated destruction of keratinocytes expressing foreign antigen Medications ▪ Most common ▪ Allopurinol, sulfa drugs (e.g. sulfonamide antibiotics), lamotrigine, carbamazepine, nevirapine, phenylbutazone, thiacetazone, oxicam NSAIDS Infections ▪ Mycoplasma pneumoniae most common infective agent RISK FACTORS HIV/AIDS Systemic lupus erythematosus > 40 years old Genetic carbamazepine interaction predisposition (HLA-B*15:02, HLAA*31:01 alleles) ▪ ↑ frequency in biological females ▪ ▪ ▪ ▪ 18 OSMOSIS.ORG Figure 3.2 An individual with Stevens– Johnson syndrome.

Chapter 3 Erythema Multiforme & Drug Eruption DIAGNOSIS SIGNS & SYMPTOMS Systemic ▪ Before skin eruptions occur ▪ Fever, sore throat, fatigue, cough Mucocutaneous ▪ Burning eyes, skin ▪ Red-purple macules → skin blisters → peels, forms painful raw areas ▪ Mucous membranes (often) → painful crusts, erosions ▪ Starts on trunk → rest of body ▪ Spontaneous ulceration of skin, mucous membranes (often eyes/lips) ▪ Conjunctivitis (often accompanied by purulent discharge) ▪ Round ulcerating lesions (approx. 2.5cm/1in diameter) ▫ Arise on face, trunk, arms, legs, soles of feet (scalp spared) ▪ Nikolsky’s sign ▪ Stevens–Johnson syndrome: < 10% skin involvement ▪ SJS/TEN overlap: 10–30% ▪ Toxic epidermal necrolysis: > 30% LAB RESULTS ▪ Skin biopsy OTHER DIAGNOSTICS ▪ Clinical history, suspected agents TREATMENT MEDICATIONS ▪ Analgesics (non-opioid for non-severe, opioids for severe pain) ▪ Antihistamines ▪ Intravenous immunoglobulin Infection control ▪ Culture-specific antibiotic initiation OTHER INTERVENTIONS ▪ ▪ ▪ ▪ Transfer to burn/intensive care unit Fluid support Oral feeding, nasogastric tube Room temperature 30–32°C/86–90°F (minimize heat loss) Infection control ▪ Sterile handling ▪ Skin disinfection ▫ Antiseptic solution ▪ 48 hourly skin, blood, indwelling line culture Figure 3.3 An individual with toxic epidermal necrolysis ten days after the onset of symptoms. OSMOSIS.ORG 19

Figure 3.4 A histological section of skin demonstrating epidermal necrolysis. The epidermis is detached from the dermis and the keratinocytes have undergone necrosis. This can be seen in erythema multiforma, Stevens-Johnson syndrom and toxic epidermal necrolysis. 20 OSMOSIS.ORG
Osmosis High-Yield Notes
This Osmosis High-Yield Note provides an overview of Erythema multiforme and drug eruption essentials. All Osmosis Notes are clearly laid-out and contain striking images, tables, and diagrams to help visual learners understand complex topics quickly and efficiently. Find more information about Erythema multiforme and drug eruption by visiting the associated Learn Page.