Cutaneous Drug Eruptions
Adverse cutaneous drug reactions (ACDRs) are common clinical challenges. They range from mild, self-limiting exanthems to life-threatening emergencies. Timely identification and cessation of the offending agent are critical.
Common Clinical Presentations
| Reaction Type | Characteristics |
|---|---|
| Exanthematous | Most common; morbilliform (measles-like) rash. Often appears 1-2 weeks after starting the drug (e.g., Penicillins). |
| Urticarial | Wheals and intense pruritus. Can be IgE-mediated (Type I hypersensitivity). |
| Fixed Drug Eruption | Reoccurs in the same site upon re-exposure. Typically dusky, violaceous plaques. |
Severe/Life-Threatening Reactions (SCARs)
- DRESS Syndrome: Drug Reaction with Eosinophilia and Systemic Symptoms (fever, lymphadenopathy, organ involvement).
- SJS/TEN: Stevens-Johnson Syndrome (< 10% skin detachment) and Toxic Epidermal Necrolysis (> 30% skin detachment). These are severe epidermal necrolytic reactions.
High-Yield Exam Pearl:
- Common Culprits: Antibiotics (Sulfa, Penicillins), Anticonvulsants (Carbamazepine, Phenytoin), and NSAIDs.
- Clinical Tip: If a rash appears shortly after starting a new medication, discontinue it immediately.
- SJS/TEN Sign: The Nikolsky sign (lateral pressure on the skin causes epidermal detachment) is positive in TEN.