Definition and Overview

DRESS Syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms) is a rare, severe systemic drug reaction characterized by dermatitis, lymphadenopathy, hematologic abnormalities (especially eosinophilia), and multiorgan involvement (hepatitis, nephritis, sometimes carditis or pneumonitis). Incidence is 1 per 1,000 to 1 per 10,000 drug exposures, with higher incidence in genetic predisposition (HLA variants). The syndrome typically manifests 2-6 weeks after initiation of the offending drug (sometimes longer), making temporal relationship less obvious than Stevens-Johnson Syndrome. Mortality ranges from 5-10% in developed countries to 20-50% in areas without access to supportive care, with deaths resulting from hepatic failure, myocarditis, or infection. DRESS syndrome is a medical emergency requiring immediate hospitalization, drug discontinuation, and systemic corticosteroids.

Epidemiology

DRESS Syndrome is rare, with incidence of 1-6 cases per 10,000 drug exposures (anticonvulsants highest). Annual incidence in developed countries ranges from 0.01 per million (UK) to 0.2 per million (Japan). Median age at presentation is 30-40 years but can occur at any age including infants. Female predominance is slight (ratio 1:1 to 1.5:1). Higher incidence reported in Asian and African populations; this may reflect genetic factors (HLA-B*5701, HLA-A*02:01 associations) or prevalence of anticonvulsant use in these populations. Prior history of drug reaction increases risk 10-25 fold if exposed to same drug or related compounds.

Causative Medications

High-risk drugs:

  • Anticonvulsants: Phenytoin (most common), carbamazepine, phenobarbital, lamotrigine, oxcarbazepine, valproic acid. Anticonvulsants account for 50-80% of DRESS cases; cross-reactivity within the class is 20-80%.
  • Allopurinol: Second most common cause; risk 1 per 1,000 exposures
  • Sulfonamides: (Trimethoprim-sulfamethoxazole) especially in HIV+ patients, 5-50 per 10,000
  • Antiretrovirals: (Nevirapine especially) 1-4 per 1,000 in resource-limited settings
  • Antimalarials: (Sulfadoxine-pyrimethamine, quinine)

Moderate-risk drugs: Antibiotics (minocycline, doxycycline, isoniazid), NSAIDs, cephalosporins, beta-blockers, calcium channel blockers, digoxin, oral contraceptives

Pathophysiology

DRESS Syndrome involves Type IV hypersensitivity with complex immunopathology: (1) Drug-specific CD8+ T cells proliferate and attack drug-modified cells; (2) Polyclonal B cell activation with hypergammaglobulinemia and autoantibodies (anti-histone, anti-nuclear, anti-dsDNA); (3) EBV and HHV-6 reactivation occurs in 50-80% of cases, possibly triggered by profound T cell dysregulation. The viral reactivation may propagate systemic inflammation. Genetic factors (HLA-B*5701, HLA-A*02:01, and other HLA alleles) predispose to drug-specific T cell expansion. The delayed onset (2-6 weeks) reflects the time required for T cell proliferation, viral reactivation, and systemic dissemination.

Clinical Presentation

Cutaneous manifestations (80-100% of cases):

  • Timing: Appears 2-6 weeks after drug initiation (sometimes longer); prolonged delay makes temporal relationship to drug less obvious than SJS
  • Morphology: Morbilliform (measles-like) rash most common (70% of cases); atypical morphologies including erythroderma, pustules, exfoliative dermatitis, or vesicular lesions occur in 20-30%
  • Distribution: Face, trunk, flexural areas initially; often spreads to involve >50% BSA
  • Associated findings: Facial edema (50% of cases), prominent facial erythema, exudative pharyngitis, oral ulcers or erosions (30% of cases), cervical lymphadenopathy palpable at time of rash onset
  • Pruritis: Severe pruritis common; often precedes rash onset

Systemic manifestations:

  • Fever: >90% of cases, typically 38-40°C, persists weeks if untreated
  • Lymphadenopathy: Cervical, axillary, or inguinal nodes enlarged (70-100% of cases); nodes may be tender
  • Hepatomegaly: 50-70% of cases; hepatitis with 2-5 fold elevation of transaminases in 50-90%; some cases develop fulminant hepatic failure
  • Splenomegaly: 10-50% of cases
  • Pulmonary involvement: Interstitial pneumonitis in 10-25%; presents as cough, dyspnea, and chest imaging showing interstitial infiltrates
  • Cardiac involvement: Myocarditis in 2-5%, may cause cardiogenic shock; pericarditis less common
  • Renal involvement: 10-15% develop acute kidney injury from interstitial nephritis; usually mild and reversible
  • Neurologic involvement: Rare but includes encephalitis, meningitis, peripheral neuropathy

Hematologic abnormalities: Eosinophilia (>1,500/μL) in 50-80%, though absence does not exclude diagnosis; atypical lymphocytes (activated T cells), thrombocytopenia in 10-30%; rarely, hemolytic anemia, DIC

Diagnosis

Diagnostic criteria (RegiSCAR scoring): Diagnosis is clinical, supported by hematologic and liver function abnormalities. RegiSCAR score ≥2 is consistent with DRESS:

  • Fever ≥38.5°C (1 point)
  • Rash extent ≥50% BSA (1 point)
  • Lymph node swelling >2cm (1 point)
  • Eosinophilia 1,500-3,000/μL (1 point) or >3,000/μL (2 points)
  • Atypical lymphocytes ≥5% (1 point) or >10% (2 points)
  • Hepatic involvement (1 point for mild, 2 for severe)
  • Negative viral serology or unusual viral reactivation (1 point)
RegiSCAR score: ≤1 = unlikely; 2-3 = possible; ≥4 = probable DRESS.

Laboratory findings: CBC shows eosinophilia and atypical lymphocytes; AST/ALT elevated 2-5 fold (80% of cases); alkaline phosphatase and bilirubin may be elevated; renal function may be abnormal; coagulation studies abnormal if hepatic dysfunction severe. Viral serology/PCR (EBV, HHV-6) may show reactivation in 50-80% of cases.

Histopathology: Skin biopsy shows superficial dermatitis with prominent eosinophilic infiltrate, sometimes with drug-induced hypersensitivity lymphadenitis pattern in lymph nodes.

Differential Diagnosis

Infectious mononucleosis: Similar presentation with pharyngitis, lymphadenopathy, eosinophilia, atypical lymphocytes. Viral serology differentiates; however, DRESS often has concurrent viral reactivation.

Acute leukemia: Eosinophilia and atypical lymphocytes may mimic leukemia; bone marrow examination differentiates.

Sepsis: Fever, systemic symptoms, and organ involvement may mimic sepsis; absence of obvious infection source, negative blood cultures, and drug temporal relationship help differentiate.

Treatment

Immediate management:

  • Drug discontinuation: Discontinue the offending drug immediately
  • Hospitalization: ICU admission for severe cases with hepatic dysfunction or cardiac/respiratory involvement
  • Supportive care: Fluid management, temperature control, nutritional support
  • Infection monitoring: Monitor for secondary infection (sepsis develops in 10-20% of cases)

Pharmacologic therapy:

  • Systemic corticosteroids: First-line therapy. Prednisone 0.5-2 mg/kg daily (or methylprednisolone 1 g daily IV for severe cases) initially, then slow taper over 6-12 weeks. Early corticosteroid therapy (within first week) significantly reduces mortality and hepatic dysfunction. Most cases respond within 1-2 weeks of corticosteroid initiation.
  • Second-line agents for steroid-refractory cases: Cyclosporine, IVIG, plasmapheresis, or other immunosuppressants in cases not responding to corticosteroids within 1-2 weeks. Limited data on efficacy.
  • Topical corticosteroids: Mid-to-high potency for cutaneous lesions
  • Antipyretics: Acetaminophen preferred (avoid NSAIDs)
  • Antihistamines: For pruritus management

Prognosis

Mortality: 5-10% in developed countries with access to early recognition and corticosteroids; higher in developing countries without timely diagnosis. Causes of death include hepatic failure, myocarditis, pneumonitis, and infection/sepsis. Mortality correlates with: degree of hepatic dysfunction (AST >200 predicts worse outcomes), multiorgan involvement, advanced age, and delayed initiation of corticosteroids.

Clinical resolution: Most cases resolve within 3-6 weeks with corticosteroid therapy, though fever may persist 1-2 weeks. Eosinophilia and atypical lymphocytes normalize over weeks to months. Hepatic function recovery occurs over weeks to months; rarely, chronic hepatitis develops.

Prevention

Risk awareness: Educate patients starting anticonvulsants, allopurinol, or other high-risk drugs about DRESS warning signs (fever, rash, swollen lymph nodes, malaise) developing 2-6 weeks after starting medication; advise immediate medical evaluation.

Cross-reactivity avoidance: 20-80% cross-reactivity exists among anticonvulsants. If DRESS develops to one anticonvulsant, avoid structurally similar anticonvulsants; choose chemically unrelated alternative.

Frequently Asked Questions

Can DRESS Syndrome develop months after taking a medication?

Typical onset is 2-6 weeks, but delayed presentations up to 6-8 weeks or occasionally longer have been reported. The prolonged delay (compared to SJS which is 1-3 weeks) reflects the time needed for drug-specific T cell proliferation and viral reactivation. If DRESS develops months after drug discontinuation, temporal relationship may be missed. Inform your physician of all medications taken in prior months if DRESS symptoms develop.

If I had DRESS Syndrome from phenytoin, can I take carbamazepine?

Cross-reactivity between anticonvulsants is significant (20-80% depending on drug pair). Carbamazepine shares similar aromatic structure with phenytoin and carries substantial re-challenge risk. Alternatives include: switching to non-aromatic anticonvulsants (valproate, levetiracetam, lamotrigine if no prior lamotrigine reaction), or careful desensitization under medical supervision in ICU setting if no alternative exists. Most physicians recommend avoiding the entire aromatic anticonvulsant class.

Is DRESS Syndrome fatal?

Mortality is 5-10% in developed countries with modern medical care and early corticosteroids. Fatalities result from fulminant hepatic failure, myocarditis, pneumonitis, or infection/sepsis. However, most cases (90-95%) survive with appropriate management. Early recognition and initiation of systemic corticosteroids significantly improves prognosis. Delay in diagnosis and treatment increases mortality substantially.

What if my DRESS Syndrome doesn't improve with corticosteroids?

Most cases respond well to corticosteroids within 1-2 weeks of initiation. If fever, rash, or systemic symptoms persist beyond 2 weeks of adequate corticosteroid therapy, consider: (1) inadequate corticosteroid dose (increase dose), (2) incorrect diagnosis (reassess for other conditions), (3) secondary infection developing, or (4) steroid-refractory DRESS (5-10% of cases). Steroid-refractory DRESS may require addition of cyclosporine, IVIG, or other second-line immunosuppressants; discuss options with your dermatologist and hepatologist.

References

  1. Kardaun SH, et al. Variability in the clinical presentation and outcome of DRESS syndrome: a prospective multicenter study. Br J Dermatol. 2007;156(3):609-611.
  2. Cacoub P, et al. The DRESS syndrome - a literature review. Am J Med. 2011;124(7):588-597.
  3. Shiohara T, et al. Drug-induced hypersensitivity syndrome (DIHS): a reaction induced by a interaction among herpesviruses, HLA, and antiviral and antidrug immune responses. Acta Derm Venereol. 2007;87(6):468-476.
  4. Descamps V, et al. Human herpesvirus 6 infection associated with drug reaction with eosinophilia and systemic symptoms syndrome. Arch Dermatol. 2001;137(10):1311-1314.
  5. Hosaka Y, et al. DRESS Syndrome with severe eosinophilia: a multicenter survey. J Dermatol. 2012;39(4):315-321.
  6. Kardaun SH, et al. Drug reaction with eosinophilia and systemic symptoms (DRESS): an original multisystem adverse drug reaction. Drug Saf. 2007;30(12):1143-1150.