What are the diagnostic criteria for DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) syndrome?

DRESS Syndrome Diagnostic Criteria

DRESS syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms) is diagnosed using the RegiSCAR scoring system, which classifies cases as "no," "possible," "probable," or "definite" based on clinical and laboratory findings. 1

Core Diagnostic Features

• DRESS syndrome typically presents after a latent period of 2-6 weeks following exposure to the offending drug, which distinguishes it from other drug reactions 2
• The most common clinical manifestations include:
  • Morbilliform (maculopapular) confluent rash involving >30% of body surface area 2
  • Facial edema 3
  • Fever (>38°C) 4
  • Lymphadenopathy 3
  • Internal organ involvement (liver, kidney, heart, lung) 2, 3

RegiSCAR Diagnostic Criteria

The diagnosis is established through a scoring system based on the following:

• Cutaneous findings:

  • Maculopapular rash involving >30% of body surface area 2, 5
  • Facial edema 5

• Systemic involvement:

  • Fever >38°C 4, 5
  • Enlarged lymph nodes (≥2 sites, >1cm) 5, 1

• Hematologic abnormalities:

  • Eosinophilia (>700/μL or >10% if leukocyte count is abnormal) 5, 1
  • Atypical lymphocytes 5

• Organ involvement:

  • Liver (ALT >2 times upper limit of normal) 4, 3
  • Kidney (creatinine >1.5 times baseline) 4, 2
  • Lung (pneumonitis, ARDS) 2
  • Heart (myocarditis, pericarditis) 2

• Other criteria:

  • Exclusion of other causes (infections, autoimmune conditions, malignancy) 5, 1
  • Resolution ≥15 days after drug withdrawal 1

Laboratory Evaluation

• Complete blood count with differential to assess for:

  • Eosinophilia 4, 5
  • Atypical lymphocytosis 5
  • Leukocytosis 2

• Comprehensive metabolic panel to evaluate:

  • Liver function (ALT, AST, alkaline phosphatase, bilirubin) 4, 3
  • Kidney function (BUN, creatinine) 4, 2

• Additional testing:

  • Urinalysis to evaluate for nephritis 4
  • Blood cultures to rule out infectious causes 4
  • Skin biopsy if diagnosis is uncertain 4

Differential Diagnosis

DRESS syndrome must be distinguished from:

• Other severe cutaneous adverse reactions:

  • Stevens-Johnson Syndrome (SJS) 2
  • Toxic Epidermal Necrolysis (TEN) 2
  • Acute Generalized Exanthematous Pustulosis (AGEP) 2

• Systemic conditions:

  • Viral infections (particularly herpes family viruses) 2
  • Autoimmune disorders 5
  • Lymphoma 5
  • Hypereosinophilic syndrome 1

Prognostic Indicators

• Poor prognostic factors include:
  • Eosinophil count >6000 × 10³/μL 5
  • Thrombocytopenia 5
  • Pancytopenia 5
  • Leukocytosis 5
  • Coagulopathy 5
  • Liver failure 6, 3

Common Pitfalls and Caveats

• Delayed diagnosis is common due to the variable presentation and latency period of 2-6 weeks after drug initiation 2, 5
• The mortality rate is estimated at 3.8-10%, primarily due to fulminant hepatitis and liver necrosis 5, 6
• Relapse can occur in approximately 12% of cases, particularly with DRESS associated with viral reactivation 2
• Certain genetic predispositions (HLA associations) are strongly linked to specific drug reactions, such as HLA-B*58:01 with allopurinol-induced DRESS 7, 2
• DRESS syndrome must be differentiated from DRESS (Drug Reaction with Eosinophilia and Systemic) syndrome, which is mentioned as a differential diagnosis for other conditions 7