DRESS syndrome and severe cutaneous reactions

SCAR Spectrum - Defining The Danger

• Stevens-Johnson Syndrome (SJS): Widespread blisters and mucosal involvement with skin detachment of <10% Body Surface Area (BSA).
• SJS/TEN Overlap: A transitional form with 10-30% BSA detachment.
• Toxic Epidermal Necrolysis (TEN): The most severe form, with >30% BSA detachment and positive Nikolsky's sign.
• DRESS Syndrome: Characterized by a long latency period (2-8 weeks), fever, extensive rash, eosinophilia, and systemic organ failure (especially liver, kidneys).

⭐ TEN carries a significantly higher mortality rate (>30%) compared to SJS (~5-10%), primarily due to sepsis from the loss of the skin barrier.

Causative Drugs - The Usual Suspects

• Anticonvulsants (Aromatic):
  • Carbamazepine, Lamotrigine, Phenytoin, Phenobarbital
• Allopurinol:
  • High risk, especially with renal impairment or diuretic use.
• Sulfonamides:
  • TMP-SMX, Sulfasalazine
• Antibiotics:
  • Minocycline, Vancomycin
• Antiretrovirals:
  • Abacavir (test for HLA-B*57:01), Nevirapine

⭐ High-Yield: Allopurinol-induced SCARs show a strong association with the HLA-B*58:01 allele, particularly in Han Chinese, Thai, and Korean populations. Consider genetic screening in these groups before initiating therapy.

Path & Presentation - Code Red Reaction

• Pathogenesis: A severe, delayed Type IVb hypersensitivity reaction. Involves drug-activated T-cells releasing cytokines (e.g., IL-5), leading to eosinophil recruitment. Frequently associated with reactivation of latent viruses like HHV-6 and EBV.

• Clinical Triad:

  • Latency: Long delay of 2-8 weeks between drug initiation and symptom onset.
  • Rash: Diffuse, morbilliform (measles-like) eruption that can become confluent, vesicular, or exfoliative. Prominent facial edema is highly characteristic.
  • Systemic Involvement: High fever, widespread lymphadenopathy, and multi-organ inflammation.

• Lab Findings:

  • Eosinophilia (>1500/μL) and atypical lymphocytes are hallmark findings.
  • Elevated liver enzymes indicate hepatitis, the most common visceral complication.

⭐ Myocarditis is a less common but highly lethal complication of DRESS syndrome, mandating a high index of suspicion in patients with chest pain or ECG changes.

Diagnosis & Action - Damage Control Protocol

• Initial Steps:

  • High index of suspicion is crucial.
  • IMMEDIATELY withdraw the offending drug.
  • Supportive care: fluids, electrolytes, nutrition.

• Confirmation:

  • Labs: CBC (↑ eosinophils, atypical lymphocytes), ↑ LFTs, ↑ creatinine.
  • Skin biopsy (punch): Confirms diagnosis (perivascular lymphocytic infiltrate, eosinophils).

• Treatment Algorithm:

⭐ Exam Favorite: DRESS syndrome is strongly associated with the reactivation of Human Herpesvirus 6 (HHV-6), which can contribute to the systemic inflammation and organ damage.

• DRESS syndrome is a drug reaction with eosinophilia and systemic symptoms, presenting with rash, fever, and internal organ (liver, kidney) damage after a long latency (2-8 weeks).
• Key triggers include allopurinol, anticonvulsants (phenytoin, carbamazepine), and sulfonamides.
• SJS/TEN are severe mucocutaneous reactions with widespread blistering, epidermal necrosis, and mucosal involvement.
• Distinguished by BSA detachment: SJS <10%, SJS-TEN overlap 10-30%, and TEN >30%.
• Management for all hinges on immediate withdrawal of the offending drug; this is the most critical step.
• Specific HLA alleles (e.g., HLA-B*1502 with carbamazepine) are major risk factors.