Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)

1. Comprehensive Introduction & Overview: Understanding DRESS Syndrome

Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) is a severe, life-threatening idiosyncratic drug reaction that represents a diagnostic challenge due to its delayed onset and multisystem involvement. Unlike typical hypersensitivity reactions that occur within hours or days, DRESS typically manifests 2 to 8 weeks after the initiation of the causative agent.

Often categorized under the umbrella of Severe Cutaneous Adverse Reactions (SCARs), DRESS is characterized by a triad of fever, rash, and internal organ involvement, accompanied by hematologic abnormalities—most notably eosinophilia and atypical lymphocytosis. Because the clinical presentation can mimic viral infections or other dermatological conditions, it is frequently misdiagnosed, leading to significant morbidity and a mortality rate estimated between 5% and 10%.

The management of DRESS requires immediate discontinuation of the culprit drug, supportive care, and, in severe cases, systemic corticosteroids or immunosuppressive agents. Early recognition is paramount to preventing long-term sequelae, including autoimmune conditions and chronic organ dysfunction.

2. Deep-Dive: Etiology and Pathophysiology

The pathophysiology of DRESS is complex, involving a delicate interplay between genetic predisposition, viral reactivation, and aberrant immune responses.

The Mechanism of Action

Current scientific consensus suggests that DRESS is a T-cell mediated delayed-type hypersensitivity reaction. The process generally follows this sequence:

1. Drug-T-Cell Interaction: The causative drug (or its metabolite) binds to human leukocyte antigen (HLA) molecules, triggering an immune response. This is often mediated via the p-i (pharmacological interaction) concept, where the drug binds directly to T-cell receptors.
2. Viral Reactivation: A unique hallmark of DRESS is the sequential reactivation of herpesviruses, specifically Human Herpesvirus 6 (HHV-6), followed by Epstein-Barr virus (EBV) and Cytomegalovirus (CMV). This viral expansion is thought to contribute to the severity of the systemic symptoms.
3. Cytokine Storm: There is an massive release of inflammatory cytokines, including IL-5 (which drives eosinophilia), IL-2, and IFN-gamma, leading to systemic inflammation and end-organ damage.

Common Culprit Agents

While many medications can trigger DRESS, the most frequent offenders are listed in the table below:

3. Clinical Indications, Presentation, and Staging

The Clinical Triad

The diagnosis of DRESS is primarily clinical, relying on the RegiSCAR scoring system. The standard presentation includes:

• Fever: Usually high-grade (38°C–40°C), often the initial symptom.
• Cutaneous Eruption: Typically a morbilliform exanthem that progresses to generalized erythroderma. Facial edema is a highly suggestive clinical sign.
• Hematologic Abnormalities: Eosinophilia (>1,500 cells/μL) and the presence of atypical lymphocytes.

Clinical Staging and Grading

While there is no universally accepted "staging" system, clinicians utilize the RegiSCAR criteria to determine the probability of DRESS:

Scoring Interpretation:
* < 2: No DRESS
* 2–3: Possible DRESS
* 4–5: Probable DRESS
* > 5: Definite DRESS

4. Differential Diagnosis

Distinguishing DRESS from other febrile exanthems is critical, as the management differs significantly.

1. Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN): These present with more severe mucosal involvement and skin sloughing rather than the morbilliform rash seen in DRESS.
2. Acute Generalized Exanthematous Pustulosis (AGEP): Characterized by numerous small, sterile pustules rather than the systemic organ involvement of DRESS.
3. Viral Exanthems: Measles, rubella, and primary HIV infection can mimic the rash but lack the marked eosinophilia and internal organ involvement.
4. Lymphoma: Persistent lymphadenopathy and hematologic changes may mimic cutaneous T-cell lymphoma (Sézary syndrome).

5. Risks, Side Effects, and Long-Term Prognosis

The prognosis of DRESS depends heavily on the extent of visceral involvement, particularly hepatitis, pneumonitis, and myocarditis.

Major Risks

• Hepatitis: The most common organ involvement; can progress to fulminant liver failure.
• Myocarditis: The leading cause of death in DRESS patients.
• Renal Failure: Often secondary to interstitial nephritis.
• Endocrine Sequelae: Studies have shown an increased risk of developing Type 1 diabetes and autoimmune thyroiditis months or years after the initial DRESS episode.

Long-Term Management

Patients who survive the acute phase require long-term monitoring. Follow-up should include:
* Serial liver function tests (LFTs).
* Thyroid function monitoring (TSH/T4).
* Avoidance of the culprit drug and structurally related compounds for life.

6. FAQ: Frequently Asked Questions

1. Is DRESS contagious?
No, DRESS is an idiosyncratic drug reaction. It is not infectious, though viral reactivation is part of its pathophysiology.

2. How long does the rash last?
The rash is often persistent and may last for several weeks, even after the causative drug is discontinued.

3. What is the role of corticosteroids?
Corticosteroids are the standard of care for moderate-to-severe DRESS to dampen the systemic inflammatory response, though there is no definitive consensus on the optimal dose or duration.

4. Can I ever take the medication again?
Absolutely not. Re-exposure to the culprit drug can lead to a rapid, life-threatening recurrence of symptoms.

5. Are there genetic tests for DRESS?
Yes, there are strong associations with specific HLA alleles (e.g., HLA-B58:01 for allopurinol, HLA-A31:01 for carbamazepine). Genetic screening is recommended before prescribing these drugs in high-risk populations.

6. Is DRESS more common in children or adults?
DRESS can occur at any age, but it is more frequently reported in adults due to higher rates of medication use.

7. Does topical treatment help?
Topical steroids and emollients are used for symptomatic relief of the skin rash but do not treat the underlying systemic pathology.

8. How is myocarditis diagnosed in DRESS?
Clinicians monitor for elevated troponin levels, ECG changes, and, if necessary, cardiac MRI to detect myocardial inflammation.

9. Why is it called "DRESS"?
The acronym was coined in 1996 by Bocquet et al. to highlight the specific combination of Drug reaction, Eosinophilia, and Systemic Symptoms.

10. What is the mortality rate?
The mortality rate is approximately 5–10%, largely driven by organ failure, specifically heart and liver complications.

7. Conclusion: Clinical Best Practices

Managing DRESS requires a multidisciplinary approach involving dermatology, internal medicine, immunology, and organ-specific specialists (e.g., hepatology, cardiology). The cornerstone of successful management remains the immediate identification and cessation of the offending drug.

Clinicians must maintain a high index of suspicion. Any patient presenting with a new rash, fever, and lymphadenopathy 2–8 weeks after starting a new medication must be evaluated for DRESS. By utilizing the RegiSCAR scoring system and monitoring for early signs of organ dysfunction, the medical team can significantly improve patient outcomes and mitigate the long-term risks associated with this complex immunologic syndrome.

For the orthopedic or specialist clinician, it is vital to remember that even "routine" medications—like allopurinol or anticonvulsants used for neuropathic pain—can be the trigger. Always review the patient’s medication history extensively when symptoms do not align with a standard infectious or localized dermatological process.