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Toronto Notes 2019 Drug Eruptions Porphyria Cutanea Tarda
Clinical Presentation
• skinfragilityfollowedbyformationoftensevesicles/bullaeanderosionsonphotoexposedskin
• gradualhealingtoscars,milia
• periorbitalviolaceousdiscolouration,diffusehypermelanosis,facialhypertrichosis
• commonsites:light-exposedareassubjectedtotrauma,dorsumofhandsandfeet,nose,andupper
trunk
Pathophysiology
• uroporphyrinogendecarboxylasedeficiencyleadstoexcesshemeprecursors
• canbeassociatedwithhemochromatosis,alcoholabuse,DM,drugs(estrogentherapy,NSAIDs),HIV,
hepatitis C, increased Fe indices
Epidemiology
• 30-40yrold,M>F
Investigations
• urineand5%HClshowsorange-redfluorescenceunderWood’slamp(UVrays) • 24hurinehaselevateduroporphyrins
• stoolcontainselevatedcoproporphyrins
• immunofluorescenceshowsIgEatdermal-epidermaljunctions
Management
• discontinueaggravatingsubstances(alcohol,estrogentherapy) • phlebotomytodecreasebodyironload
• lowdosehydroxychloroquine
Drug Eruptions
Exanthematous
EXANTHEMATOUS DRUG REACTION
Clinical Presentation
• morphology:erythematousmaculesandpapules±scale
• spread: symmetrical, trunk to extremities
• timecourse:7-14dafterdruginitiation,fades7-14dafterwithdrawal
Epidemiology
• mostcommoncutaneousdrugreaction;increasedinpresenceofinfections • commoncausativeagents:penicillin,sulfonamides,phenytoin
Management
• weighrisksandbenefitsofdrugdiscontinuation • antihistamines, emollients, topical steroids
DRUG INDUCED HYPERSENSITIVITY SYNDROME (DIHS) / DRUG REACTION WITH EOSINOPHILIA AND SYSTEMIC SYMPTOMS (DRESS)
Clinical Presentation
• morphology:morbilliformrashinvolvingface,trunk,arms;canhavefacialedema
• systemicfeatures:fever,malaise,cervicallymphadenopathy,internalorganinvolvement(e.g.
hepatitis, arthralgia, nephritis, pneumonitis, lymphadenopathy, hematologic abnormalities, thyroid
abnormalities)
• spread:startswithfaceorperiorbitallyandspreadscaudally;nomucosalinvolvement
• timecourse:onset1-6wkafterfirstexposuretodrug;persistswkafterwithdrawalofdrug
Epidemiology
• rare:incidencevariesconsiderablydependingondrug
• commoncausativeagents:anticonvulsants(e.g.phenytoin,phenobarbital,carbamazepine,lamotrigine),
sulfonamides, and allopurinol
• 10%mortalityifsevere,undiagnosed,anduntreated
Management
• discontinueoffendingdrug±prednisone0.5mg/kg/d,considercyclosporineinseverecases • mayprogresstogeneralizedexfoliativedermatitis/erythrodermaifdrugisnotdiscontinued
Dermatology D21
Diagnosis of a Drug Reaction
Classification by Naranjo et. al has 4 criteria: 1. Temporal relationship between drug
exposure and reaction
2. Recognized response to suspected drug 3. Improvement after drug withdrawal
4. Recurrence of reaction on re-challenge
with the drug
Definite drug reaction requires all 4 criteria to be met
Probable drug reaction requires #1-3 to be met
Possible drug reaction requires only #1
Drug Hypersensitivity Syndrome Triad
• Fever
• Exanthematous eruption • Internal organ involvement