Which of the following is classified as a Type E adverse reaction?

Rebound effect due to drug withdrawal

A 42-year-old man was seen in the clinic because of pain and redness in his finger. Last week he had injured the finger while working in his garage. On physical examination, there is erythema, swelling, and tenderness of the second digit in the right hand. Flexion and extension of the finger were normal. A clinical diagnosis of cellulitis is made and he is prescribed cephalexin. A few days later he presents to the emergency room complaining of difficulty breathing. He has angioedema due to a drug reaction to the cephalexin. Which of the following physical findings is characteristic of this syndrome?

Involvement of lips, tongue, eyelids, genitalia, and dorsum of hands or feet

Fluid extravasation from subcutaneous and intradermal postcapillary venules

Adverse Cutaneous Drug Reactions for FMGE: High-Yield Dermatology Lessons

Introduction & Common Patterns - Rash Decisions

Adverse Cutaneous Drug Reactions (ACDRs): Unintended skin reactions to drugs at normal therapeutic doses.

Classification:
- Type A (Augmented): Dose-dependent, predictable (e.g., side effects). Constitute ~80% of ADRs.
- Type B (Bizarre): Dose-independent, unpredictable, often immune-mediated (e.g., allergy).
Immunological Basis: Primarily Type IV (e.g., exanthematous eruptions) & Type I (e.g., urticaria) hypersensitivity reactions.
Common Patterns:
- Exanthematous (Maculopapular): Most frequent. Symmetrical, itchy, morbilliform rash.
- Urticaria/Angioedema: Wheals (hives), localized dermal/subcutaneous swelling.
- Fixed Drug Eruption (FDE): Recurrent, well-demarcated, dusky erythematous or violaceous plaques appearing at the same site(s) upon re-exposure. Common causes: NSAIDs, sulfonamides, tetracyclines.

⭐ Exanthematous drug eruptions are the most common type of ACDR, typically appearing 4-14 days after initiating the offending drug, often accompanied by mild eosinophilia and pruritus.

Severe Cutaneous Adverse Reactions (SCARs) - Skin Under Siege

SCARs are severe, potentially life-threatening drug eruptions. Prompt diagnosis and drug withdrawal are crucial.

Feature	Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)	Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)	Acute Generalized Exanthematous Pustulosis (AGEP)
Onset	4-28 days	2-8 weeks (delayed)	<4 days (rapid)
Skin	Dusky red macules, atypical targets, Nikolsky +. BSA: SJS <10%, SJS/TEN 10-30%, TEN >30%	Morbilliform rash, facial edema	Numerous small, sterile, non-follicular pustules on edematous erythema. Often flexural.
Mucosal	Severe, ≥2 sites	Common, often mild	Rare/mild
Systemic	Fever, ↑LFTs, cytopenias. SCORTEN score (0-7) for prognosis.	Fever, marked eosinophilia, atypical lymphocytes, lymphadenopathy, multi-organ (liver, kidney, lung)	High fever, neutrophilia
Common Drugs	Allopurinol, Lamotrigine, NSAIDs, Sulfonamides	Allopurinol, Anticonvulsants, Sulfonamides	Beta-lactams, Macrolides
📌 Mnemonic		📌 Drug Rash Eosinophilia Systemic Symptoms

⭐ SCORTEN score (0-7 points) is crucial for prognosis in SJS/TEN; each point significantly increases mortality risk.

Causative Drugs & Associations - Pill Problem Profiles

Common drugs implicated in Adverse Cutaneous Drug Reactions (ACDRs) and their typical manifestations:

Drug/Class	Key ACDR(s)
Penicillins	Maculopapular rash, Urticaria, Angioedema
Sulphonamides	Morbilliform, FDE, SJS/TEN, DRESS 📌 Sulpha: SCARs, FDE
Aromatic Anticonvulsants	SJS/TEN, DRESS (Phenytoin, Carbamazepine, Lamotrigine)
Allopurinol	Maculopapular rash, DRESS, SJS/TEN
NSAIDs	Urticaria, Angioedema, Photosensitivity, FDE, SJS/TEN
Vancomycin	Red Man Syndrome (infusion-related, non-allergic)
ACE Inhibitors	Angioedema (can be delayed)
Tetracyclines	Photosensitivity, FDE
Antiretrovirals (ART)	Nevirapine (rash, SJS/TEN), Abacavir (HSR, HLA-B*5701)
Antitubercular (ATT)	Rif (DRESS, orange fluids), INH (Pellagra), PZA (Photosens.)

Diagnosis & Management - Reaction Resolution

Diagnosis:
- Drug history: Onset, all meds (Rx, OTC, herbal).
- Clinical exam: Lesion morphology, distribution, severity (SCORTEN for SJS/TEN).
- Investigations: Skin biopsy (pattern), patch tests (Type IV), IgE (Type I), CBC (eosinophilia), LFTs, RFTs.
Management Principles:
- IMMEDIATE WITHDRAWAL of suspected drug(s).
- Supportive: Hydration, nutrition, wound care, antihistamines, analgesia.
Specific Therapies:
- Morbilliform: Topical/oral steroids, antihistamines.
- SJS/TEN: ICU. Systemic steroids (early, controversial), IVIG, Cyclosporine.
- DRESS: Systemic steroids (mainstay, slow taper).
Resolution & Prevention:
- Monitor. Gradual drug taper. Educate: avoid re-exposure, cross-reactivity. Document.
⭐ In DRESS, systemic corticosteroids are mainstay; slow taper over weeks/months prevents relapse.

High‑Yield Points - ⚡ Biggest Takeaways

Morbilliform rash: Most common cutaneous drug reaction.

SJS/TEN: Severe, life-threatening; key drugs: allopurinol, carbamazepine, lamotrigine, sulfonamides.

DRESS syndrome: Fever, rash, eosinophilia, lymphadenopathy, internal organ involvement (liver, kidney).

Fixed Drug Eruption (FDE): Recurrent, well-demarcated plaques at the same site on re-exposure.

AGEP: Sudden widespread sterile pustules, fever; often due to antibiotics (beta-lactams).

Photosensitivity: Phototoxic (sunburn-like, common) vs. Photoallergic (eczematous, delayed).

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play