Drug rash

Background

ABCs of Drug Rashes

• Acute generalized exanthematous pustulosis (AGEP)
• Bullous disease, drug induced
• Captopril (ACE-inhibitor) induced angioedema
• Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome
• SJS/TEN

Rash Red Flags

• Fever
• Toxic appearance
• Hypotension
• Mucosal lesions
• Severe pain
• Very old or young age
• Immunosuppressed
• New medication

Clinical Features

Morbilliform drug eruption on back

• Sudden, usually morbilliform, often starts on face & trunk & spreads
• More polymorphous than viral exanthem

Differential Diagnosis

Erythematous rash

• Positive Nikolsky’s sign
  • Febrile
    • Staphylococcal scalded skin syndrome (children)
    • Toxic epidermal necrolysis/SJS (adults)
  • Afebrile
    • Toxic epidermal necrolysis
• Negative Nikolsky’s sign
  • Febrile
    • Toxic shock syndrome
    • Kawasaki disease
    • Scarlet fever
    • DRESS syndrome
    • Cellulitis
    • Acute generalized exanthematous pustulosis
  • Afebrile
    • Alcohol intoxication
    • Anaphylaxis
    • Cellulitis
    • Dermatitis (multiple types)
    • Drug rash
    • Erysipelas
    • Erythema multiforme
    • Exfoliative erythroderma
    • Scombroid
    • Vancomycin infusion reaction

Evaluation

• Typically a clinical diagnosis

Table of Severe Drug Rashes

Charateristic	DRESS	SJS/TEN	AGEP	Erythroderma
Image
Onset of eruption	2-6 weeks	1-3 weeks	48 hours	1-3 weeks
Duration of eruption (weeks)	Several	1-3	<1	Several
Fever	+++	+++	+++	+++
Mucocutaneous features	Facial edema, morbilliform eruption, pustules, exfoliative dermattiis, tense bullae, possible target lesions	Bullae, atypical target lesions, mucocutaneous erosions	Facial edema, pustules, tense bullae, possible target lesions, possibl emucosal involvement	Erythematous plaques and edema affecting >90% of total skin surface with or without diffuse exfoliation
Lymph node enlargement	+++	-	+	+
Neutrophils	Elevated	Decreased	Very elevated	Elevated
Eosinophils	Very elevated	No change	Elevated	Elevated
Atypical lymphocytes	+	-	-	+
Hepatitis	+++	++	++	-
Other organ involvement	Interstitial nephritis, pneumonitis, myocarditis, and thydoiditis	Tubular nephritis and tracheobronical necrosis	Possible	Possible
Histological pattern of skin	Perivascular lymphocytcic infiltrate	Epidermal necrosis	Subcorneal pustules	Nonspecific, unless reflecting Sezary syndrome or other lymphoma
Lymph node histology	Lymphoid hyperplasia	-	-	No, unless reflecting Sezary syndrome or other malignancy
Mortality (%)	10	5-35	5	5-15

Management

• Discontinue offending agent
• Supportive
• Topical steroids may help relieve pruritus

Disposition

• If no signs of anaphylaxis or significant sloughing, consider outpatient management

See Also

• Erythematous rash